An earlier commit made GDB no longer assume no-debug-info functions
return int. This commit gives the same treatment to variables.
Currently, you can end misled by GDB over output like this:
(gdb) p var
$1 = -1
(gdb) p /x var
$2 = 0xffffffff
until you realize that GDB is assuming that the variable is an "int",
because:
(gdb) ptype var
type = <data variable, no debug info>
You may try to fix it by casting, but that doesn't really help:
(gdb) p /x (unsigned long long) var
$3 = 0xffffffffffffffff # incorrect
^^
That's incorrect output, because the variable was defined like this:
uint64_t var = 0x7fffffffffffffff;
^^
What happened is that with the cast, GDB did an int -> 'unsigned long
long' conversion instead of reinterpreting the variable as the cast-to
type. To get at the variable properly you have to reinterpret the
variable's address manually instead, with either:
(gdb) p /x *(unsigned long long *) &var
$4 = 0x7fffffffffffffff
(gdb) p /x {unsigned long long} &var
$5 = 0x7fffffffffffffff
After this commit GDB does it for you. This is what you'll get
instead:
(gdb) p var
'var' has unknown type; cast it to its declared type
(gdb) p /x (unsigned long long) var
$1 = 0x7fffffffffffffff
As in the functions patch, the "compile" machinery doesn't currently
have the cast-to type handy, so it continues assuming no-debug
variables have int type, though now at least it warns.
The change to gdb.cp/m-static.exp deserves an explanation:
- gdb_test "print 'gnu_obj_1::method()::sintvar'" "\\$\[0-9\]+ = 4" \
+ gdb_test "print (int) 'gnu_obj_1::method()::sintvar'" "\\$\[0-9\]+ = 4" \
That's printing the "sintvar" function local static of the
"gnu_obj_1::method()" method.
The problem with that test is that that "'S::method()::static_var'"
syntax doesn't really work in C++ as you'd expect. The way to make it
work correctly currently is to quote the method part, not the whole
expression, like:
(gdb) print 'gnu_obj_1::method()'::sintvar
If you wrap the whole expression in quotes, like in m-static.exp, what
really happens is that the parser considers the whole string as a
symbol name, but there's no debug symbol with that name. However,
local statics have linkage and are given a mangled name that demangles
to the same string as the full expression, so that's what GDB prints.
After this commit, and without the cast, the print in m-static.exp
would error out saying that the variable has unknown type:
(gdb) p 'gnu_obj_1::method()::sintvar'
'gnu_obj_1::method()::sintvar' has unknown type; cast it to its declared type
TBC, if currently (even before this series) you try to print any
function local static variable of type other than int, you'll get
bogus results. You can see that with m-static.cc as is, even.
Printing the "svar" local, which is a boolean (1 byte) still prints as
"int" (4 bytes):
(gdb) p 'gnu_obj_1::method()::svar'
$1 = 1
(gdb) ptype 'gnu_obj_1::method()::svar'
type = <data variable, no debug info>
This probably prints some random bogus value on big endian machines.
If 'svar' was of some aggregate type (etc.) we'd still print it as
int, so the problem would have been more obvious... After this
commit, you'll get instead:
(gdb) p 'gnu_obj_1::method()::svar'
'gnu_obj_1::method()::svar' has unknown type; cast it to its declared type
... so at least GDB is no longer misleading. Making GDB find the real
local static debug symbol is the subject of the following patches. In
the end, it'll all "Just Work".
gdb/ChangeLog:
2017-09-04 Pedro Alves <palves@redhat.com>
* ax-gdb.c: Include "typeprint.h".
(gen_expr_for_cast): New function.
(gen_expr) <OP_CAST, OP_CAST_TYPE>: Use it.
<OP_VAR_VALUE, OP_MSYM_VAR_VALUE>: Error out if the variable's
type is unknown.
* dwarf2read.c (new_symbol_full): Fallback to int instead of
nodebug_data_symbol.
* eval.c: Include "typeprint.h".
(evaluate_subexp_standard) <OP_VAR_VALUE, OP_VAR_MSYM_VALUE>:
Error out if symbol has unknown type.
<UNOP_CAST, UNOP_CAST_TYPE>: Common bits factored out to
evaluate_subexp_for_cast.
(evaluate_subexp_for_address, evaluate_subexp_for_sizeof): Handle
OP_VAR_MSYM_VALUE.
(evaluate_subexp_for_cast): New function.
* gdbtypes.c (init_nodebug_var_type): New function.
(objfile_type): Use it to initialize types of variables with no
debug info.
* typeprint.c (error_unknown_type): New.
* typeprint.h (error_unknown_type): New declaration.
* compile/compile-c-types.c (convert_type_basic): Handle
TYPE_CODE_ERROR; warn and fallback to int for variables with
unknown type.
gdb/testsuite/ChangeLog:
2017-09-04 Pedro Alves <palves@redhat.com>
* gdb.asm/asm-source.exp: Add casts to int.
* gdb.base/nodebug.c (dataglobal8, dataglobal32_1, dataglobal32_2)
(dataglobal64_1, dataglobal64_2): New globals.
* gdb.base/nodebug.exp: Test different expressions involving the
new globals, with print, whatis and ptype. Add casts to int.
* gdb.base/solib-display.exp: Add casts to int.
* gdb.compile/compile-ifunc.exp: Expect warning. Add cast to int.
* gdb.cp/m-static.exp: Add cast to int.
* gdb.dwarf2/dw2-skip-prologue.exp: Add cast to int.
* gdb.threads/tls-nodebug.exp: Check that gdb errors out printing
tls variable with no debug info without a cast. Test with a cast
to int too.
* gdb.trace/entry-values.exp: Add casts.
PR gdb/21675 points out a few regressions in scalar printing.
One type of regression is due to not carrying over the old handling of
floating point printing -- where a format like "/d" causes a floating
point number to first be cast to a signed integer. This patch restores
this behavior.
The other regression is a longstanding bug in print_octal_chars: one of
the constants was wrong. This patch fixes the constant and adds static
asserts to help catch this sort of error.
ChangeLog
2017-08-14 Tom Tromey <tom@tromey.com>
PR gdb/21675
* valprint.c (LOW_ZERO): Change value to 034.
(print_octal_chars): Add static_asserts for octal constants.
* printcmd.c (print_scalar_formatted): Add 'd' case.
testsuite/ChangeLog
2017-08-14 Tom Tromey <tom@tromey.com>
PR gdb/21675:
* gdb.base/printcmds.exp (test_radices): New function.
* gdb.dwarf2/var-access.exp: Use p/u, not p/d.
* gdb.base/sizeof.exp (check_valueof): Use p/d.
* lib/gdb.exp (get_integer_valueof): Use p/d.
This Rust bug report:
https://github.com/rust-lang/rust/issues/41970
noted an error from gdb. What is happening here (for me, the original
report had a different error) is that a pieced DWARF expression is not
writing to every byte in the resulting value. GDB errors in this
case. However, it seems to me that it is always valid to write fewer
bytes; the issue comes from writing too many -- that is, the test is
reversed. The test was also checking the sub-object, but this also
seems incorrect, as it's expected for the expression to write the
entirety of the enclosing object. So, this patch reverses the test
and applies it to the outer type, not the subobject type.
Regtested on the buildbot.
gdb/ChangeLog
2017-07-09 Tom Tromey <tom@tromey.com>
* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): Reverse size
check and apply to outer type.
gdb/testsuite/ChangeLog
2017-07-09 Tom Tromey <tom@tromey.com>
* gdb.dwarf2/shortpiece.exp: New file.
In some cases a compiler may produce a single object file (& thus single
DWO file) representing multiple source files. The most common example of
this is in whole program optimization (such as LLVM's LTO). Fission may
still be a beneficial feature to use here - to avoid the need to
read/link the debug info with system libraries and the like.
This change adds basic support for multiple CUs in a single DWO file to
support LLVM's output in this situation.
There is still outstanding work to design and implement a solution for
cross-CU references (usually using DW_FORM_ref_addr) in this scenario.
For now LLVM works around this by duplicating DIEs rather than making
cross-CU references in DWO files. This degrades debugger
behavior/quality especially for file-local entities.
2017-07-06 David Blaikie <dblaikie@gmail.com>
* dwarf2read.c (struct dwo_file): Use a htab of dwo_unit* (rather than
a singular dwo_unit*) to support multiple CUs in the same way that
multiple TUs are supported.
(create_cus_hash_table): Replace create_dwo_cu with a function for
parsing multiple CUs from a DWO file.
(open_and_init_dwo_file): Use create_cus_hash_table rather than
create_dwo_cu.
(lookup_dwo_cutu): Lookup CU in the hash table in the dwo_file with
htab_find, rather than comparing the signature to a singleton CU in
the dwo_file.
2017-07-06 David Blaikie <dblaikie@gmail.com>
* gdb.dwarf2/fission-multi-cu.S: Test containing multiple CUs in a DWO,
built from fissiont-multi-cu{1,2}.c.
* gdb.dwarf2/fission-multi-cu.exp: Test similar to fission-base.exp,
except putting 'main' and 'func' in separate CUs in the same DWO file.
* gdb.dwarf2/fission-multi-cu1.c: First CU for the multi-CU-single-DWO
test.
* gdb.dwarf2/fission-multi-cu2.c: Second CU in the multi-CU-single-DWO
test.
The new test var-access.exp causes FAILs on i686. This is because the
test chooses the wrong name for DWARF register number 1: It uses
"edx" (which corresponds to DWARF register number 2), but should have used
"ecx" instead.
Also, the current logic in var-access.exp does not correctly distinguish
between a 64-bit and a 32-bit program on an x86-64 target. It uses the
64-bit register names for both.
These problems are fixed. In order to address the latter, the convenience
macros is_*_target are exploited where appropriate.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/var-access.exp: Use register name ecx instead of edx
on 32-bit x86 targets. Exploit is_*_target macros where
appropriate.
So far GDB ignores the piece offset of all kinds of DWARF bit
pieces (DW_OP_bit_piece) and treats such pieces as if the offset was zero.
This is fixed, and an appropriate test is added.
gdb/ChangeLog:
* dwarf2loc.c (read_pieced_value): Respect the piece offset, as
given by DW_OP_bit_piece.
(write_pieced_value): Likewise.
Andreas Arnez <arnez@linux.vnet.ibm.com>
* gdb.dwarf2/var-access.exp: Add test for composite location with
nonzero piece offsets.
For big-endian targets the logic in read/write_pieced_value tries to take
a register piece from the LSB end. This requires offsets and sizes to be
adjusted accordingly, and that's where the current implementation has some
issues:
* The formulas for recalculating the bit- and byte-offsets into the
register are wrong. They just happen to yield correct results if
everything is byte-aligned and the piece's last byte belongs to the
given value.
* After recalculating the bit offset into the register, the number of
bytes to be copied from the register is not recalculated. Of course
this does not matter if everything (particularly the piece size) is
byte-aligned.
These issues are fixed. The size calculation is performed with a new
helper function bits_to_bytes().
gdb/ChangeLog:
* dwarf2loc.c (bits_to_bytes): New function.
(read_pieced_value): Fix offset calculations for register pieces
on big-endian targets.
(write_pieced_value): Likewise.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/var-access.exp: Add test for non-byte-aligned
register pieces.
This verifies some of the previous fixes to the logic in
write_pieced_value when accessing bit-fields.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/var-access.exp: Add tests for accessing bit-fields
located in one or more DWARF pieces.
The test suite contains multiple instances of determining the target's
endianness with GDB's "show endian" command. This patch replaces these by
an invocation of a new convenience proc 'get_endianness'.
gdb/testsuite/ChangeLog:
* lib/gdb.exp (get_endianness): New proc.
* gdb.arch/aarch64-fp.exp: Use it.
* gdb.arch/altivec-regs.exp: Likewise.
* gdb.arch/e500-regs.exp: Likewise.
* gdb.arch/vsx-regs.exp: Likewise.
* gdb.base/dump.exp: Likewise.
* gdb.base/funcargs.exp: Likewise.
* gdb.base/gnu_vector.exp: Likewise.
* gdb.dwarf2/formdata16.exp: Likewise.
* gdb.dwarf2/implptrpiece.exp: Likewise.
* gdb.dwarf2/nonvar-access.exp: Likewise.
* gdb.python/py-inferior.exp: Likewise.
* gdb.trace/unavailable-dwarf-piece.exp: Likewise.
When taking a DW_OP_piece or DW_OP_bit_piece from a DW_OP_stack_value, the
existing logic always takes the piece from the lowest-addressed end, which
is wrong on big-endian targets. The DWARF standard states that the
"DW_OP_bit_piece operation describes a sequence of bits using the least
significant bits of that value", and this also matches the current logic
in GCC. For instance, the GCC guality test case pr54970.c fails on s390x
because of this.
This fix adjusts the piece accordingly on big-endian targets. It is
assumed that:
* DW_OP_piece shall take the piece from the LSB end as well;
* pieces reaching outside the stack value bits are considered undefined,
and a zero value can be used instead.
gdb/ChangeLog:
PR gdb/21226
* dwarf2loc.c (read_pieced_value): Anchor stack value pieces at
the LSB end, independent of endianness.
gdb/testsuite/ChangeLog:
PR gdb/21226
* gdb.dwarf2/nonvar-access.exp: Add checks for verifying that
stack value pieces are taken from the LSB end.
A field f in a structure composed of DWARF pieces may be located in
multiple pieces, where the first and last of those may contain bits from
other fields as well. So when writing to f, the beginning of the first
and the end of the last of those pieces may have to be skipped. But the
logic in write_pieced_value for handling one of those pieces is flawed
when the first and last piece are the same, i.e., f is contained in a
single piece:
< - - - - - - - - - piece_size - - - - - - - - - ->
+-------------------------------------------------+
| skipped_bits | f_bits | / / / / / / / / / / |
+-------------------------------------------------+
The current logic determines the size of the sub-piece to operate on by
limiting the piece size to the bit size of f and then subtracting the
skipped bits:
min (piece_size, f_bits) - skipped_bits
Instead of:
min (piece_size - skipped_bits, f_bits)
So the resulting sub-piece size is corrupted, leading to wrong handling of
this piece in write_pieced_value.
Note that the same bug was already found in read_pieced_value and fixed
there (but not in write_pieced_value), see PR 15391.
This patch swaps the calculations, bringing them into the same (correct)
order as in read_pieced_value.
gdb/ChangeLog:
* dwarf2loc.c (write_pieced_value): Fix order of calculations for
size capping.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/var-pieces.exp: Add test case for modifying a
variable at nonzero offset.
This adds a test for read/write access to variables with various types of
DWARF locations. It uses register- and memory locations and composite
locations with register- and memory pieces.
Since the new test calls gdb_test_no_output with commands that contain
braces, it is necessary for string_to_regexp to quote braces as well.
This was not done before.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/var-access.c: New file.
* gdb.dwarf2/var-access.exp: New test.
* lib/gdb-utils.exp (string_to_regexp): Quote braces as well.
Recently I fixed a bug that caused a DW_OP_implicit_pointer with non-zero
offset into a DW_OP_implicit_value to be handled incorrectly on big-endian
targets. GDB ignored the offset and copied the wrong bytes:
https://sourceware.org/ml/gdb-patches/2017-01/msg00251.html
But there is still a similar issue when a DW_OP_implicit_pointer points
into a DW_OP_stack_value instead; and again, the offset is ignored. There
is an important difference, though: While implicit values are treated like
blocks of data and anchored at the lowest-addressed byte, stack values
traditionally contain integer numbers and are anchored at the *least
significant* byte. Also, stack values do not come in varying sizes, but
are cut down appropriately when used. Thus, on big-endian targets the
scenario looks like this (higher addresses shown right):
|<- - - - - Stack value - - - - - - ->|
| |
|<- original object ->|
|
| offset ->|####|
^^^^
de-referenced
implicit pointer
(Note how the original object's size influences the position of the
de-referenced implicit pointer within the stack value. This is not the
case for little-endian targets, where the original object starts at offset
zero within the stack value.)
This patch implements the logic indicated in the above diagram and adds an
appropriate test case. A new function dwarf2_fetch_die_type_sect_off is
added; it is used for retrieving the original object's type, so its size
can be determined. That type is passed to dwarf2_evaluate_loc_desc_full
via a new parameter.
gdb/ChangeLog:
* dwarf2loc.c (indirect_synthetic_pointer): Get data type of
pointed-to DIE and pass it to dwarf2_evaluate_loc_desc_full.
(dwarf2_evaluate_loc_desc_full): New parameter subobj_type; rename
byte_offset to subobj_byte_offset. Fix the handling of
DWARF_VALUE_STACK on big-endian targets when coming via an
implicit pointer.
(dwarf2_evaluate_loc_desc): Adjust call to
dwarf2_evaluate_loc_desc_full.
* dwarf2loc.h (dwarf2_fetch_die_type_sect_off): New declaration.
* dwarf2read.c (dwarf2_fetch_die_type_sect_off): New function.
gdb/testsuite/ChangeLog:
* lib/dwarf.exp: Add support for DW_OP_implicit_pointer.
* gdb.dwarf2/nonvar-access.exp: Add test for stack value location
and implicit pointer into such a location.
DWARF-5 has new form DW_FORM_data16. The problem is that GDB cannot pass
16-byte constant as a constant value as that would require GDB to use GCC
extension __int128.
Formerly such data was coded as DW_FORM_block* so GDB still decodes
DW_FORM_data16 like DW_FORM_block*.
gdb/ChangeLog
2017-02-20 Jan Kratochvil <jan.kratochvil@redhat.com>
* dwarf2read.c (skip_one_die, read_attribute_value)
(dwarf2_const_value_attr, dump_die_shallow)
(dwarf2_get_attr_constant_value, dwarf2_fetch_constant_bytes)
(skip_form_bytes, attr_form_is_constant): Handle DW_FORM_data16.
gdb/testsuite/ChangeLog
2017-02-20 Jan Kratochvil <jan.kratochvil@redhat.com>
* gdb.dwarf2/formdata16.c: New file.
* gdb.dwarf2/formdata16.exp: New file.
* lib/dwarf.exp (Dwarf): Add DW_FORM_data16.
The test case implptrpiece.exp accesses the second byte of the short
integer number 1 and expects it to be zero. This is valid for
little-endian targets, but fails on big-endian targets.
This is fixed by distinguishing the expected value by endianness.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/implptrpiece.exp: Fix check for big-endian targets.
When a variable's location is expressed as DW_OP_implicit_value, but the
given value is longer than needed, which bytes should be used? GDB's
current logic was introduced with a patch from 2011 and uses the "least
significant" bytes:
https://sourceware.org/ml/gdb-patches/2011-08/msg00123.html
Now consider a sub-value from such a location at a given offset, accessed
through DW_OP_implicit_pointer. Which bytes should be used for that? The
patch above *always* uses the last bytes on big-endian targets, ignoring
the offset.
E.g., given the code snippet
const char foo[] = "Hello, world!";
const char *a = &foo[0];
const char *b = &foo[7];
assume that `foo' is described as DW_OP_implicit_value and `a' and `b'
each as DW_OP_implicit_pointer into that value. Then with current GDB
`*a' and `*b' yield the same result -- the string's zero terminator.
This patch basically reverts the portion of the patch above that deals
with DW_OP_implicit_value. This fixes the offset handling and also goes
back to dropping the last instead of the first bytes on big-endian targets
if the implicit value is longer than needed. The latter aspect of the
change probably doesn't matter for actual programs, but simplifies the
logic.
The patch also cleans up the original code a bit and adds appropriate test
cases.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-op-stack-value.exp: Adjust expected result of
taking a 2-byte value out of a 4-byte DWARF implicit value on
big-endian targets.
* gdb.dwarf2/nonvar-access.exp: Add more comments to existing
logic. Add test cases for DW_OP_implicit.
gdb/ChangeLog:
* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): For
DWARF_VALUE_LITERAL, no longer ignore the offset on big-endian
targets. And if the implicit value is longer than needed, extract
the first bytes instead of the "least significant" ones.
This patch adds a DW_OP_implicit_value in dwarf assembler, and uses
dwarf assembler in implptr-64bit.exp. Using dwarf assembler in
implptr-64bit.exp exposes some limitations in dwarf assembler,
- some variables are not evaluated in the caller's context, so we
can not pass variable to assembler, like this
Dwarf::assemble $asm_file {
cu {
version $dwarf_version
addr_size $addr_size
is_64 $is_64
} {
}
and
{DW_AT_type :$struct_label "DW_FORM_ref$ref_addr_size"}
this limitation is fixed by adding "uplevel" and "subst".
- dwarf assembler doesn't emit DW_FORM_ref_addr for label referencing.
this limitation is fixed by adding a new character "%",
{ type %$int_label }
this means we want to emit DW_FORM_ref_addr for label referencing.
- we can't set the form of label referencing offset in dwarf assembler.
Nowadays, dwarf assembler guesses the form of labels, which is
DW_FORM_ref4. However, in implptr-64bit.exp, both DW_FORM_ref4
and DW_FORM_ref8 is used (see REF_ADDR in implptr-64bit.S). This
patch adds the flexibility of setting the form of label reference.
Both of them below are valid,
{DW_AT_type :$struct_label}
{DW_AT_type :$struct_label DW_FORM_ref8}
the former form is the default DW_FORM_ref4.
I compared the .debug_info of objects without and with this patch
applied. There is no changes except abbrev numbers.
gdb/testsuite:
2017-01-25 Andreas Arnez <arnez@linux.vnet.ibm.com>
Yao Qi <yao.qi@linaro.org>
* gdb.dwarf2/implptr-64bit.exp: Use dwarf assembler.
* gdb.dwarf2/implptr-64bit.S: Remove.
* lib/dwarf.exp (Dwarf): Handle character "%". Evaluate some
variables in caller's context. Add DW_OP_implicit_value.
This applies the second part of GDB's End of Year Procedure, which
updates the copyright year range in all of GDB's files.
gdb/ChangeLog:
Update copyright year range in all GDB files.
This patch adds support for DW_AT_main_subprogram.
This is PR symtab/16264.
DW_AT_main_subprogram is used to mark a program's entry point. GCC
can emit this, and I hope to change the Rust compiler to emit it as
well.
GDB already supports an older, pre-DWARF 4 convention adopted by
FORTRAN compilers, namely to emit DW_AT_calling_convention for the
"main" function. However, I think this support in GDB had a small
bug, in that it seems to rely on the DW_AT_name being read before
DW_AT_calling_convention. This patch fixes this as well.
Built and regtested on x86-64 Fedora 24 and the buildbot. New test
case included.
2016-12-02 Tom Tromey <tom@tromey.com>
PR symtab/16264:
* dwarf2read.c (struct partial_die_info) <main_subprogram>: New
member.
(add_partial_symbol): Call set_objfile_main_name.
(read_partial_die): Handle DW_AT_main_subprogram.
<DW_AT_calling_convention>: don't call set_objfile_main_name, but
set main_subprogram flag.
2016-12-02 Tom Tromey <tom@tromey.com>
* gdb.dwarf2/main-subprogram.c: New file.
* gdb.dwarf2/main-subprogram.exp: New file.
When the user writes or reads a variable whose location is described
with DWARF pieces (DW_OP_piece or DW_OP_bit_piece), GDB's helper
function copy_bitwise is invoked for each piece. The implementation of
this function has a bug that may result in a corrupted copy, depending
on alignment and bit size. (Full-byte copies are not affected.)
This rewrites copy_bitwise, replacing its algorithm by a fixed version,
and adding an appropriate test case. Without the fix the new test case
fails, e.g.:
print def_t
$2 = {a = 0, b = 4177919}
(gdb) FAIL: gdb.dwarf2/nonvar-access.exp: print def_t
Written in binary, the wrong result above looks like this:
01111111011111111111111
Which means that two zero bits have sneaked into the copy of the
original all-one bit pattern. The test uses this simple all-one value
in order to avoid another GDB bug that causes the DWARF piece of a
DW_OP_stack_value to be taken from the wrong end on big-endian
architectures.
gdb/ChangeLog:
* dwarf2loc.c (extract_bits_primitive): Remove.
(extract_bits): Remove.
(copy_bitwise): Rewrite. Fixes a possible corruption that may
occur for non-byte-aligned copies.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/nonvar-access.exp: Add a test for accessing
non-byte-aligned bit fields.
The DW_AT_data_bit_offset attribute was introduced by DWARF V4 and
allows specifying the offset of a data member within its containing
entity. But although the new attribute was intended to replace
DW_AT_bit_offset for this purpose, GDB ignores it, and thus GCC still
emits DW_AT_bit_offset instead. See also
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71669.
This change fixes GDB's lack of support for DW_AT_data_bit_offset and
adds an appropriate test case.
gdb/ChangeLog:
PR gdb/12616
* dwarf2read.c (dwarf2_add_field): Handle the DWARF V4 attribute
DW_AT_data_bit_offset.
gdb/testsuite/ChangeLog:
PR gdb/12616
* gdb.dwarf2/nonvar-access.exp: New testcase. Check that GDB
respects the DW_AT_data_bit_offset attribute.
The "struct S" type in bitfield-parent-optimized-out.exp is declared to
have a size of 4 bytes but to hold two 4-byte members: an int-based
bitfield and a 4-byte int. Also, both members have the same
data_member_location 2, causing them to overlap and to reach 2 bytes
beyond the structure's boundary.
This is fixed by increasing the structure size to 8 and setting the
first and second member's data_member_location to 0 and 4, respectively.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/bitfield-parent-optimized-out.exp: Fix DWARF code for
the definition of struct S.
With something like:
struct A { int bitfield:4; } var;
If 'var' ends up wholly-optimized out, printing 'var.bitfield' crashes
gdb here:
(top-gdb) bt
#0 0x000000000058b89f in extract_unsigned_integer (addr=0x2 <error: Cannot access memory at address 0x2>, len=2, byte_order=BFD_ENDIAN_LITTLE)
at /home/pedro/gdb/mygit/src/gdb/findvar.c:109
#1 0x00000000005a187a in unpack_bits_as_long (field_type=0x16cff70, valaddr=0x0, bitpos=16, bitsize=12) at /home/pedro/gdb/mygit/src/gdb/value.c:3347
#2 0x00000000005a1b9d in unpack_value_bitfield (dest_val=0x1b5d9d0, bitpos=16, bitsize=12, valaddr=0x0, embedded_offset=0, val=0x1b5d8d0)
at /home/pedro/gdb/mygit/src/gdb/value.c:3441
#3 0x00000000005a2a5f in value_fetch_lazy (val=0x1b5d9d0) at /home/pedro/gdb/mygit/src/gdb/value.c:3958
#4 0x00000000005a10a7 in value_primitive_field (arg1=0x1b5d8d0, offset=0, fieldno=0, arg_type=0x16d04c0) at /home/pedro/gdb/mygit/src/gdb/value.c:3161
#5 0x00000000005b01e5 in do_search_struct_field (name=0x1727c60 "bitfield", arg1=0x1b5d8d0, offset=0, type=0x16d04c0, looking_for_baseclass=0, result_ptr=0x7fffffffcaf8,
[...]
unpack_value_bitfield is already optimized-out/unavailable -aware:
(...) VALADDR points to the contents of VAL. If the VAL's contents
required to extract the bitfield from are unavailable/optimized
out, DEST_VAL is correspondingly marked unavailable/optimized out.
however, it is not considering the case of the value having no
contents buffer at all, as can happen through
allocate_optimized_out_value.
gdb/ChangeLog:
2016-08-09 Pedro Alves <palves@redhat.com>
* value.c (unpack_value_bitfield): Skip unpacking if the parent
has no contents buffer to begin with.
gdb/testsuite/ChangeLog:
2016-08-09 Pedro Alves <palves@redhat.com>
* gdb.dwarf2/bitfield-parent-optimized-out.exp: New file.
Marin Cermak has found various testcases (or one of them) of GDB FAIL on
ppc64.
https://sourceware.org/bugzilla/show_bug.cgi?id=20328
.o contained only the function descriptor address.
The DWARF as produced by Tcl Dwarf::assemble:
<1><27>: Abbrev Number: 4 (DW_TAG_subprogram)
<28> DW_AT_name : main
<2d> DW_AT_external : 1
<2e> DW_AT_low_pc : 0x1001ff98
<36> DW_AT_high_pc : 0x1002ff98
<2><3e>: Abbrev Number: 5 (DW_TAG_lexical_block)
Runtime info:
$2 = {<text variable, no debug info>} 0x10000674 <.main>
$3 = {void ()} 0x1001ff98 <main>
On Tue, 12 Jul 2016 15:22:49 +0200, Ulrich Weigand wrote:
Well, most of the gdb.dwarf2 test cases simply use explicitly placed labels
for the DW_AT_low_pc / DW_AT_high_pc attributes.
See e.g. dw2-unresolved-main.c:
asm (".globl cu_text_start");
asm ("cu_text_start:");
On Wed, 13 Jul 2016 10:54:00 +0200, Jan Kratochvil wrote:
Now I see I should not do that because:
lib/dwarf.exp:
proc function_range { func src } {
So I am providing this patch.
gdb/testsuite/ChangeLog
2016-07-13 Jan Kratochvil <jan.kratochvil@redhat.com>
* gdb.dwarf2/atomic-type.exp: Use function_range for low_pc and high_pc.
* gdb.dwarf2/atomic.c (f): Rename f_end_lbl to f_label.
* gdb.dwarf2/dw2-bad-mips-linkage-name.c (f): Rename f_end_lbl to
f_label.
(g): Rename g_end_lbl to g_label.
* gdb.dwarf2/dw2-bad-mips-linkage-name.exp: Use function_range for
low_pc and high_pc.
* gdb.dwarf2/dw2-lexical-block-bare.exp: Likewise.
https://sourceware.org/bugzilla/show_bug.cgi?id=19893
I've traced the main source of the problem to pieced_value_funcs.coerce_ref not being
implemented. Since gdb always assumes references are implemented as pointers, this
causes it to think that it's dealing with a NULL pointer, thus breaking any operations
involving synthetic references.
What I did here was implementing pieced_value_funcs.coerce_ref using some of the synthetic
pointer handling code from indirect_pieced_value, as Pedro suggested. I also made a few
adjustments to the reference printing code so that it correctly shows either the address
of the referenced value or (if it's non-addressable) the "<synthetic pointer>" string.
I also wrote some unit tests based on Dwarf::assemble; these took a while to make
because in most cases I needed a synthetic reference to a physical variable. Additionally,
I started working on a unit test for classes that have a vtable, but ran into a few issues
so that'll probably go in a future patch. One thing that should definitely be fixed is that
proc function_range (called for MACRO_AT_func) will always try to compile/link using gcc
with the default options instead of g++, thus breaking C++ compilations that require e.g. libstdc++.
gdb/ChangeLog:
* dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer,
fetch_const_value_from_synthetic_pointer): New functions.
(indirect_pieced_value): Move lower half to indirect_synthetic_pointer.
(pieced_value_funcs): Implement coerce_ref.
* valops.c (value_addr): Call coerce_ref for synthetic references.
* valprint.c (valprint_check_validity): Return true for synthetic
references. Also, don't show "<synthetic pointer>" if they reference
addressable values.
(generic_val_print_ref): Handle synthetic references. Also move some
code to print_ref_address.
(print_ref_address, get_value_addr_contents): New functions.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/implref.exp: Rename to...
* gdb.dwarf2/implref-const.exp: ...this. Also add more test statements.
* gdb.dwarf2/implref-array.c: New file.
* gdb.dwarf2/implref-array.exp: Likewise.
* gdb.dwarf2/implref-global.c: Likewise.
* gdb.dwarf2/implref-global.exp: Likewise.
* gdb.dwarf2/implref-struct.c: Likewise.
* gdb.dwarf2/implref-struct.exp: Likewise.
Local variables in lambdas are not accessible
https://sourceware.org/bugzilla/show_bug.cgi?id=15231
GDB: read_lexical_block_scope
/* Ignore blocks with missing or invalid low and high pc attributes. */
[...]
if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, cu, NULL))
return;
But sometimes there is:
FAIL: gcc-5.3.1-6.fc23.x86_64
<2><92>: Abbrev Number: 11 (DW_TAG_lexical_block)
<3><9c>: Abbrev Number: 13 (DW_TAG_structure_type)
<9d> DW_AT_name : (indirect string, offset: 0x3c): <lambda()>
[...]
Where DW_TAG_lexical_block has no attributes. Such whole subtree is currently
dropped by GDB while I think it should just import all its children DIEs.
It even XFAIL->XPASSes gdb.ada/out_of_line_in_inlined.exp:
commit 0fa7fe506c
Author: Joel Brobecker <brobecker@adacore.com>
out of line functions nested inside inline functions.
So I have removed that xfail.
gdb/ChangeLog
2016-05-30 Jan Kratochvil <jan.kratochvil@redhat.com>
PR c++/15231
* dwarf2read.c (enum pc_bounds_kind): Add PC_BOUNDS_INVALID.
(process_psymtab_comp_unit_reader, read_func_scope): Adjust callers.
(read_lexical_block_scope): Import DIEs from bare DW_TAG_lexical_block.
(read_call_site_scope): Adjust callers.
(dwarf2_get_pc_bounds): Implement pc_bounds_invalid.
(dwarf2_get_subprogram_pc_bounds, get_scope_pc_bounds): Adjust callers.
gdb/testsuite/ChangeLog
2016-05-30 Jan Kratochvil <jan.kratochvil@redhat.com>
PR c++/15231
* gdb.ada/out_of_line_in_inlined.exp: Remove xfails.
* gdb.dwarf2/dw2-lexical-block-bare.exp: New file.
gdb/ChangeLog:
* dwarf2loc.c (dwarf2_find_location_expression): For DWO files still
add base_offset.
gdb/testsuite/ChangeLog:
* lib/dwarf.exp (build_executable_from_fission_assembler): Pass
$options when building executable.
* gdb.dwarf2/fission-loclists-pie.c: New file.
* gdb.dwarf2/fission-loclists-pie.exp: New file.
PR symtab/19914
* dwarf2read.c (open_and_init_dwp_file): Look at backlink if objfile
is separate debug file.
testsuite/
* gdb.dwarf2/dwp-sepdebug.c: New file.
* gdb.dwarf2/dwp-sepdebug.exp: New file.
After compiling a program which uses C++ references some optimizations may
convert the references into synthetic "pointers". Trying to print the address
of one of such synthetic references causes gdb to crash with the following
error:
(gdb) print &ref
/build/buildd/gdb-7.7.1/gdb/dwarf2loc.c:1624: internal-error: Should not be able to create a lazy value with an enclosing type
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Apparently, what was causing it was that value_addr returns a copy of the value
that represents the reference with its type set to T* instead of T&. However,
its enclosing_type is left untouched, which fails a check made in
read_pieced_value. We only see the crash happen for references that are
synthetic because they're treated as pieced values, thus the call to
read_pieced_value.
On a related note, it seems that in general there are all sorts of breakage
when working with synthetic references. This is reported here:
https://sourceware.org/bugzilla/show_bug.cgi?id=19893
gdb/ChangeLog:
2016-04-18 Martin Galvan <martin.galvan@tallertechnologies.com>
* valops.c (value_addr): For C++ references, set the copied value's
enclosing_type as well.
gdb/testsuite/ChangeLog:
2016-04-18 Martin Galvan <martin.galvan@tallertechnologies.com>
* gdb.dwarf2/implref.exp: New file.
This patch implements a test that ensures that with "set print object
on", -var-create returns "<optimized out>" for an optimized out pointer
to structure, rather than throwing an error, while also ensuring that
any attempt to dereference the pointer *will* throw an error.
It uses the dwarf assembler to construct the appropriate debug info
to represent a pointer-to-struct in the program as optimized out,
and then accesses that pointer in various ways. The test uses both
the console interpreter and the MI interpreter.
gdb/testsuite/ChangeLog:
2016-04-06 Don Breazeal <donb@codesourcery.com>
* gdb.dwarf2/dw2-opt-structptr.c: New test program.
* gdb.dwarf2/dw2-opt-structptr.exp: New test script.
When running tests in parallel, each test puts its generated files in a
different directory, under "outputs". I think it would be nice if it
was always the case, as it would isolate the test cases a bit more. An
artifact created by a test wouldn't get overwritten by another test.
Also, it makes it easier to clean up. A lot of executables are left all
over the place because their names do not appear in gdb.*/Makefile. If
everything is in "outputs", then we just have to delete that directory
(which we already do).
At the same time it makes the gdb.foo directories and their Makefiles
useless in the build directory, since they are pretty much only used for
cleaning.
What do you think?
gdb/testsuite/ChangeLog:
* Makefile.in (ALL_SUBDIRS): Remove.
(clean mostlyclean): Do not recurse in ALL_SUBDIRS.
(distclean maintainer-clean realclean): Likewise.
* configure.ac (AC_OUTPUT): Remove gdb.*/Makefile.
* configure: Regenerate.
* gdb.ada/Makefile.in: Delete.
* gdb.arch/Makefile.in: Likewise.
* gdb.asm/Makefile.in: Likewise.
* gdb.base/Makefile.in: Likewise.
* gdb.btrace/Makefile.in: Likewise.
* gdb.cell/Makefile.in: Likewise.
* gdb.compile/Makefile.in: Likewise.
* gdb.cp/Makefile.in: Likewise.
* gdb.disasm/Makefile.in: Likewise.
* gdb.dlang/Makefile.in: Likewise.
* gdb.dwarf2/Makefile.in: Likewise.
* gdb.fortran/Makefile.in: Likewise.
* gdb.gdb/Makefile.in: Likewise.
* gdb.go/Makefile.in: Likewise.
* gdb.guile/Makefile.in: Likewise.
* gdb.java/Makefile.in: Likewise.
* gdb.linespec/Makefile.in: Likewise.
* gdb.mi/Makefile.in: Likewise.
* gdb.modula2/Makefile.in: Likewise.
* gdb.multi/Makefile.in: Likewise.
* gdb.objc/Makefile.in: Likewise.
* gdb.opencl/Makefile.in: Likewise.
* gdb.opt/Makefile.in: Likewise.
* gdb.pascal/Makefile.in: Likewise.
* gdb.perf/Makefile.in: Likewise.
* gdb.python/Makefile.in: Likewise.
* gdb.reverse/Makefile.in: Likewise.
* gdb.server/Makefile.in: Likewise.
* gdb.stabs/Makefile.in: Likewise.
* gdb.threads/Makefile.in: Likewise.
* gdb.trace/Makefile.in: Likewise.
* gdb.xml/Makefile.in: Likewise.
* lib/gdb.exp (make_gdb_parallel_path): Add check for
GDB_PARALLEL.
(standard_output_file): Remove check for GDB_PARALLEL, always
return path in outputs/$subdir/$testname.
It is possible to use multiple base addresses within a single address
range series, within the .debug_ranges section. The following is a
simplified example for 32-bit addresses:
.section ".debug_ranges"
.4byte 0xffffffff
.4byte BASE_1
.4byte START_OFFSET_1
.4byte END_OFFSET_1
.4byte START_OFFSET_2
.4byte END_OFFSET_2
.4byte 0xffffffff
.4byte BASE_2
.4byte START_OFFSET_3
.4byte END_OFFSET_3
.4byte 0
.4byte 0
In this example START/END 1 and 2 are relative to BASE_1, while
START/END 3 are relative to BASE_2.
Currently gdb does not correctly parse this DWARF, resulting in
corrupted address range information. This commit fixes this issue, and
adds a new test to cover this case.
In order to support testing of this feature extensions were made to the
testsuite dwarf assembler, additional functionality was added to the
.debug_line generation function, and a new function for generating the
.debug_ranges section was added.
gdb/ChangeLog:
* dwarf2read.c (dwarf2_ranges_read): Unify and fix base address
reading code.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-ranges-base.c: New file.
* gdb.dwarf2/dw2-ranges-base.exp: New file.
* lib/dwarf.exp (namespace eval Dwarf): Add new variables to
support additional line table, and debug ranges generation.
(Dwarf::ranges): New function, generate .debug_ranges.
(Dwarf::lines): Support generating simple line table programs.
(Dwarf::assemble): Initialise new namespace variables.
Some of the source code for the test cases in the GDB testsuite
reside in .S files containing assembly code. These files typically
define a symbol - such as main - which may, depending on the target,
require a prefix such as underscore.
For example, gdb.dwarf2/dw-compdir-oldgcc.S defines the symbol main:
main: .globl main
Some targets, such as rx-elf, require main to have an underscore
prefix. (If it doesn't, a linker error results due to not being able
to find _main required by crt0.o.) So, instead, the above should look
like this for rx-elf and other targets with this same requirement:
_main: .globl _main
This patch defines a new tcl proc in lib/gdb named
gdb_target_symbol_prefix_flags_asm. This proc returns a string
which will - assuming everything else is wired up correctly - cause
-DSYMBOL_PREFIX=_ to be passed on the command line to the compiler.
The test cases are augmented with a macro definition for SYMBOL
as follows:
#define CONCAT1(a, b) CONCAT2(a, b)
#define CONCAT2(a, b) a ## b
#ifdef SYMBOL_PREFIX
# define SYMBOL(str) CONCAT1(SYMBOL_PREFIX, str)
#else
# define SYMBOL(str) str
#endif
Symbols, such as main shown in the example earlier are then wrapped
with SYMBOL like this:
SYMBOL(main): .globl SYMBOL(main)
The net effect will be to add a prefix for those targets which need
it and add no prefix for those targets which do not.
It should be noted that there was already a proc in lib/gdb.exp
called gdb_target_symbol_prefix_flags. It still exists, but has
been significantly rewritten. (There is only one small difference
between the two versions.)
That proc used to explicitly list targets which were known to
require an underscore prefix. This is no longer done; the recently
added proc, gdb_target_symbol_prefix, is now invoked to dynamically
discover whether or not a prefix is required for that particular
target.
The difference between gdb_target_symbol_prefix_flags_asm
and gdb_target_symbol_prefix_flags is that the former returns
a bare prefix while the latter returns the prefix enclosed in
double quotes. I.e. assuming that the discovered prefix is
underscore, gdb_target_symbol_prefix_flags_asm returns:
additional_flags=-DSYMBOL_PREFIX=_
while gdb_target_symbol_prefix_flags returns:
additional_flags=-DSYMBOL_PREFIX="_"
The double-quoted version is not suitable for using with .S files
containing assembly code; there is no way to strip the double quotes
using C preprocessor constructs.
It would be possible to use the bare (non double quoted) version in
C source code. However, the supporting macros become more complicated
and therefore more difficult to maintain.
gdb/testsuite/ChangeLog:
* lib/gdb (gdb_target_symbol_prefix_flags_asm): New proc.
(gdb_target_symbol_prefix_flags): Define in terms of _asm
version.
* gdb.arch/i386-float.exp, gdb.arch/i386-permbkpt.exp,
gdb.dwarf2/dw2-canonicalize-type.exp,
gdb.dwarf2/dw2-compdir-oldgcc.exp, gdb.dwarf2/dw2-minsym-in-cu.exp,
gdb.dwarf2/dw2-op-stack-value.exp, gdb.dwarf2/dw2-unresolved.exp,
gdb.dwarf2/fission-reread.exp, gdb.dwarf2/pr13961.exp: Use flags
provided by gdb_target_symbol_prefix_flags_asm.
* gdb.dwarf2/dw2-canonicalize-type.S, gdb.dwarf2/dw2-compdir-oldgcc.S,
testsuite/gdb.dwarf2/dw2-minsym-in-cu.S,
testsuite/gdb.dwarf2/dw2-unresolved-main.c,
testsuite/gdb.dwarf2/dw2-unresolved.S, gdb.dwarf2/fission-reread.S,
gdb.dwarf2/pr13961.S: Define and use SYMBOL macro (and supporting
macros where needed). Use this macro for symbols which require
the prefix provided by SYMBOL_PREFIX.
Some of the tests in gdb.dwarf2 which use Dwarf::assemble refer to
(minimal/linker) symbols created in the course of building a small
test program. Some targets use a prefix such as underscore ("_") on
these symbols. Many of the tests in gdb.dwarf2 do not take this into
account. As a consequence, these tests fail to build, resulting
either in failures or untested testcases.
Here is an example from gdb.dwarf2/dw2-regno-invalid.exp:
Dwarf::assemble $asm_file {
cu {} {
compile_unit {
{low_pc main DW_FORM_addr}
{high_pc main+0x10000 DW_FORM_addr}
} {
...
}
For targets which require an underscore prefix on linker symbols,
the two occurrences of "main" would have to have a prepended underscore,
i.e. _main instead of main.
For the above case, a call to the new proc gdb_target_symbol is used
prepend the correct prefix to the symbol. I.e. the above code is
rewritten (as shown in the patch) as follows:
Dwarf::assemble $asm_file {
cu {} {
compile_unit {
{low_pc [gdb_target_symbol main] DW_FORM_addr}
{high_pc [gdb_target_symbol main]+0x10000 DW_FORM_addr}
} {
...
}
I also found it necessary to make an adjustment to lib/dwarf.exp so that
expressions of more than just one list element can be used in DW_TAG_...
constructs. Both atomic-type.exp and dw2-bad-mips-linkage-name.exp require
this new functionality.
gdb/testsuite/ChangeLog:
* lib/gdb.exp (gdb_target_symbol_prefix, gdb_target_symbol):
New procs.
* lib/dwarf.exp (_handle_DW_TAG): Handle attribute values,
representing expressions, of more than one list element.
* gdb.dwarf2/atomic-type.exp (Dwarf::assemble): Use gdb_target_symbol
to prepend linker symbol prefix to f.
* gdb.dwarf2/data-loc.exp (Dwarf::assemble): Likewise, for
table_1 and table_2.
* gdb.dwarf2/dw2-bad-mips-linkage-name.exp (Dwarf::assemble):
Likewise, for f and g.
* gdb.dwarf2/dw2-ifort-parameter.exp (Dwarf::assemble): Likewise,
for ptr.
* gdb.dwarf2/dw2-regno-invalid.exp (Dwarf::assemble): Likewise,
for main.
* gdb.dwarf2/dynarr-ptr.exp (Dwarf::assemble): Likewise, for
table_1_ptr and table_2_ptr.
2015-10-02 Sandra Loosemore <sandra@codesourcery.com>
gdb/testsuite/
* gdb.dwarf2/staticvirtual.exp: Generalize regexp so it can match
whether or not address 0x1000 is mapped on the target.
bfd/ChangeLog:
* targets.c (enum bfd_flavour): Add comment.
(bfd_flavour_name): New function.
* bfd-in2.h: Regenerate.
gdb/ChangeLog:
* findvar.c (default_read_var_value) <LOC_UNRESOLVED>: Include the
kind of minimal symbol in the error message.
* objfiles.c (objfile_flavour_name): New function.
* objfiles.h (objfile_flavour_name): Declare.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-bad-unresolved.c: New file.
* gdb.dwarf2/dw2-bad-unresolved.exp: New file.
Here, in dwarfread.c:process_full_comp_unit:
/* Set symtab language to language from DW_AT_language. If the
compilation is from a C file generated by language preprocessors, do
not set the language if it was already deduced by start_subfile. */
if (!(cu->language == language_c
&& COMPUNIT_FILETABS (cust)->language != language_c))
COMPUNIT_FILETABS (cust)->language = cu->language;
in case start_subfile doesn't manage to deduce a language
COMPUNIT_FILETABS(cust)->language ends up as language_unknown, not
language_c. So the condition above evals false and we never set the
language from the cu's language.
gdb/ChangeLog:
2015-08-20 Pedro Alves <palves@redhat.com>
* dwarf2read.c (process_full_comp_unit): To tell whether
start_subfile managed to deduce a language, test for
language_unknown instead of language_c.
gdb/testsuite/ChangeLog:
2015-08-20 Pedro Alves <palves@redhat.com>
* gdb.dwarf2/comp-unit-lang.exp: New file.
* gdb.dwarf2/comp-unit-lang.c: New file.
This change introduces a new function, dwarf2_string_attr(), which is
a wrapper for dwarf2_attr(). dwarf2read.c has been updated to
call dwarf2_string_attr in most instances where a string-valued
attribute is decoded to produce a string value. In most cases, it
simplifies the code; in some instances, the complexity of the code
remains unchanged.
I performed this change by looking for instances where the
result of DW_STRING was used in an assignment. Many of these
had a pattern which (roughly) looks something like this:
struct attribute *attr = NULL;
attr = dwarf2_attr (die, name, cu);
if (attr != NULL && DW_STRING (attr))
{
const char *str;
...
str = DW_STRING (attr);
... /* Use str in some fashion. */
}
Code of this form is transformed to look like this instead:
const char *str;
str = dwarf2_string_attr (die, name, cu)
if (str != NULL)
{
...
/* Use str in some fashion. */
...
}
In addition to invoking dwarf2_attr() and DW_STRING(),
dwarf2_string_attr() checks to make sure that the attribute's
`form' field matches one of DW_FORM_strp, DW_FORM_string, or
DW_FORM_GNU_strp_alt. If it does not match one of these forms,
it will return a NULL value in addition to calling complaint().
An earlier version of this patch did this type checking for one
particular instance where a string attribute was being decoded.
The situation that I was attempting to handle in that earlier patch is
this:
The Texas Instruments compiler uses the encoding for
DW_AT_MIPS_linkage_name for other purposes. TI uses the encoding,
0x2007, for TI_AT_TI_end_line which, unlike DW_AT_MIPS_linkage_name,
does not have a string-typed value. In this instance, GDB was attempting
to use an integer value as a string pointer, with predictable results.
(GDB would die with a segmentation fault.)
I've added a test which reproduces the problem that I was orignally
wanting to fix. It uses DW_AT_MIPS_linkage name with an associate
value which is a string, and again, where the value is a small
integer.
My test case causes GDB to segfault in an unpatched GDB. There
will be two PASSes in a patched GDB.
Unpatched GDB:
(gdb) ptype f
ERROR: Process no longer exists
UNRESOLVED: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype f
ERROR: Couldn't send ptype g to GDB.
UNRESOLVED: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype g
Patched GDB:
(gdb) ptype f
type = bool ()
(gdb) PASS: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype f
ptype g
type = bool ()
(gdb) PASS: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype g
I see no regressions on an x86_64 native target.
gdb/ChangeLog:
* dwarf2read.c (dwarf2_string_attr): New function.
(lookup_dwo_unit, process_psymtab_comp_unit_reader)
(dwarf2_compute_name, dwarf2_physname, find_file_and_directory)
(read_call_site_scope, namespace_name, guess_full_die_structure_name)
(anonymous_struct_prefix, prepare_one_comp_unit): Use
dwarf2_string_attr in place of dwarf2_attr and DW_STRING.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-bad-mips-linkage-name.c: New file.
* gdb.dwarf2/dw2-bad-mips-linkage-name.exp: New file.
Dummy CUs are used by the incremental linker to pre-allocate space
in the output file. They have a DWARF header but no contents.
gdb/ChangeLog:
* dwarf2read.c (dwarf2_per_cu_data): Add comment.
(load_cu): Handle dummy CUs.
(dw2_do_instantiate_symtab, process_queuef): Ditto.
(dwarf2_fetch_die_loc_sect_off, dwarf2_fetch_constant_bytes): Ditto.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-dummy-cu.S: New file.
* gdb.dwarf2/dw2-dummy-cu.exp: New file.
Pedro Alves
Tom Tromey
David Blaikie
Andreas Arnez
Jan Kratochvil
Yao Qi
Joel Brobecker
Luis Machado
Martin Galvan
Doug Evans
Don Breazeal
Simon Marchi
Andrew Burgess
Kevin Buettner
Sandra Loosemore
Doug Evans