[gdb/symtab] Prefer var def over decl
Consider the DWARF as generated by gcc with the tentative patch to fix gcc
PR91507 - "wrong debug for completed array with previous incomplete
declaration":
...
<1><f4>: Abbrev Number: 2 (DW_TAG_array_type)
<f5> DW_AT_type : <0xff>
<f9> DW_AT_sibling : <0xff>
<2><fd>: Abbrev Number: 3 (DW_TAG_subrange_type)
<2><fe>: Abbrev Number: 0
<1><ff>: Abbrev Number: 4 (DW_TAG_pointer_type)
<100> DW_AT_byte_size : 8
<101> DW_AT_type : <0x105>
<1><105>: Abbrev Number: 5 (DW_TAG_base_type)
<106> DW_AT_byte_size : 1
<107> DW_AT_encoding : 6 (signed char)
<108> DW_AT_name : (indirect string, offset: 0x19f): char
<1><10c>: Abbrev Number: 6 (DW_TAG_variable)
<10d> DW_AT_name : zzz
<111> DW_AT_decl_file : 1
<112> DW_AT_decl_line : 1
<113> DW_AT_decl_column : 14
<114> DW_AT_type : <0xf4>
<118> DW_AT_external : 1
<118> DW_AT_declaration : 1
<1><118>: Abbrev Number: 2 (DW_TAG_array_type)
<119> DW_AT_type : <0xff>
<11d> DW_AT_sibling : <0x128>
<1><12f>: Abbrev Number: 8 (DW_TAG_variable)
<130> DW_AT_specification: <0x10c>
<134> DW_AT_decl_line : 2
<135> DW_AT_decl_column : 7
<136> DW_AT_type : <0x118>
<13a> DW_AT_location : 9 byte block: 3 30 10 60 0 0 0 0 0 (DW_OP_addr: 601030)
...
The DWARF will result in two entries in the symbol table, a decl with type
char *[] and a def with type char*[2].
When trying to print the value of zzz:
...
$ gdb a.spec.out -batch -ex "p zzz"
...
the decl (rather than the def) will be found in the symbol table, which is
missing the location information, and consequently we get:
...
$1 = 0x601030 <zzz>
...
[ There is a fallback mechanism that finds the address of the variable in the
minimal symbol table, but that's not used here, because the type of the decl
does not specify a size. We could use the symbol size here to get the size
of the type, but that's currently not done: PR exp/24989. Still, fixing that
PR would not fix the generic case, where minimal symbol info is not
available. ]
Fix this by preferring defs over decls when searching in the symbol table.
Build and reg-tested on x86_64-linux.
gdb/ChangeLog:
2019-12-06 Tom de Vries <tdevries@suse.de>
PR symtab/24971
* block.c (best_symbol, better_symbol): New function.
(block_lookup_symbol_primary, block_lookup_symbol): Prefer def over
decl.
gdb/testsuite/ChangeLog:
2019-12-06 Tom de Vries <tdevries@suse.de>
* gdb.dwarf2/varval.exp: Add decl before def test.
Change-Id: Id92326cb8ef9903b121ef9e320658eb565d0f5a9
This commit is contained in:
Tom de Vries
parent
e8dc9b5bfd
commit
93e55f0a03
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@ -1,3 +1,10 @@
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2019-12-06 Tom de Vries <tdevries@suse.de>
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PR symtab/24971
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* block.c (best_symbol, better_symbol): New function.
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(block_lookup_symbol_primary, block_lookup_symbol): Prefer def over
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decl.
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2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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* gdbtypes.h: Define the REFERENCE_SEE_THROUGH_BADNESS value.
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74
gdb/block.c
74
gdb/block.c
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@ -657,6 +657,43 @@ block_iter_match_next (const lookup_name_info &name,
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return block_iter_match_step (iterator, name, 0);
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}
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/* Return true if symbol A is the best match possible for DOMAIN. */
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static bool
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best_symbol (struct symbol *a, const domain_enum domain)
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{
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return (SYMBOL_DOMAIN (a) == domain
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&& SYMBOL_CLASS (a) != LOC_UNRESOLVED);
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}
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/* Return symbol B if it is a better match than symbol A for DOMAIN.
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Otherwise return A. */
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static struct symbol *
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better_symbol (struct symbol *a, struct symbol *b, const domain_enum domain)
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{
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if (a == NULL)
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return b;
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if (b == NULL)
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return a;
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if (SYMBOL_DOMAIN (a) == domain
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&& SYMBOL_DOMAIN (b) != domain)
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return a;
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if (SYMBOL_DOMAIN (b) == domain
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&& SYMBOL_DOMAIN (a) != domain)
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return b;
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if (SYMBOL_CLASS (a) != LOC_UNRESOLVED
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&& SYMBOL_CLASS (b) == LOC_UNRESOLVED)
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return a;
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if (SYMBOL_CLASS (b) != LOC_UNRESOLVED
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&& SYMBOL_CLASS (a) == LOC_UNRESOLVED)
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return b;
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return a;
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}
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/* See block.h.
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Note that if NAME is the demangled form of a C++ symbol, we will fail
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@ -684,7 +721,9 @@ block_lookup_symbol (const struct block *block, const char *name,
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ALL_BLOCK_SYMBOLS_WITH_NAME (block, lookup_name, iter, sym)
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{
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if (SYMBOL_DOMAIN (sym) == domain)
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/* See comment related to PR gcc/debug/91507 in
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block_lookup_symbol_primary. */
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if (best_symbol (sym, domain))
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return sym;
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/* This is a bit of a hack, but symbol_matches_domain might ignore
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STRUCT vs VAR domain symbols. So if a matching symbol is found,
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@ -692,7 +731,7 @@ block_lookup_symbol (const struct block *block, const char *name,
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exactly the same domain. PR 16253. */
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if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
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SYMBOL_DOMAIN (sym), domain))
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other = sym;
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other = better_symbol (other, sym, domain);
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}
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return other;
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}
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@ -746,7 +785,34 @@ block_lookup_symbol_primary (const struct block *block, const char *name,
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sym != NULL;
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sym = mdict_iter_match_next (lookup_name, &mdict_iter))
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{
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if (SYMBOL_DOMAIN (sym) == domain)
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/* With the fix for PR gcc/debug/91507, we get for:
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...
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extern char *zzz[];
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char *zzz[ ] = {
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"abc",
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"cde"
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};
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...
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DWARF which will result in two entries in the symbol table, a decl
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with type char *[] and a def with type char *[2].
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If we return the decl here, we don't get the value of zzz:
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...
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$ gdb a.spec.out -batch -ex "p zzz"
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$1 = 0x601030 <zzz>
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...
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because we're returning the symbol without location information, and
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because the fallback that uses the address from the minimal symbols
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doesn't work either because the type of the decl does not specify a
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size.
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To fix this, we prefer def over decl in best_symbol and
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better_symbol.
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In absence of the gcc fix, both def and decl have type char *[], so
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the only option to make this work is improve the fallback to use the
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size of the minimal symbol. Filed as PR exp/24989. */
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if (best_symbol (sym, domain))
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return sym;
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/* This is a bit of a hack, but symbol_matches_domain might ignore
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@ -755,7 +821,7 @@ block_lookup_symbol_primary (const struct block *block, const char *name,
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exactly the same domain. PR 16253. */
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if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
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SYMBOL_DOMAIN (sym), domain))
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other = sym;
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other = better_symbol (other, sym, domain);
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}
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return other;
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@ -1,3 +1,7 @@
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2019-12-06 Tom de Vries <tdevries@suse.de>
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* gdb.dwarf2/varval.exp: Add decl before def test.
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2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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* gdb.cp/rvalue-ref-overload.exp: Minor cleanup.
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@ -55,7 +55,8 @@ proc setup_exec { arg_bad } {
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var_b_label var_c_label var_p_label var_bad_label \
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varval_label var_s_label var_untyped_label \
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var_a_abstract_label var_a_concrete_label \
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varval2_label
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varval2_label varval3_def_label varval3_decl_label \
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int_array_label int_array_of_1_label
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set int_size [get_sizeof "int" -1]
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@ -171,6 +172,32 @@ proc setup_exec { arg_bad } {
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{DW_AT_location {DW_OP_addr [gdb_target_symbol "var_b"]} SPECIAL_expr}
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}
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int_array_label: DW_TAG_array_type {
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{DW_AT_type :${int_label}}
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} {
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DW_TAG_subrange_type {}
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}
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varval3_decl_label: DW_TAG_variable {
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{DW_AT_name "varval3"}
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{DW_AT_type :${int_array_label}}
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{DW_AT_external 1 DW_FORM_flag}
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{DW_AT_declaration 1 DW_FORM_flag}
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}
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int_array_of_1_label: DW_TAG_array_type {
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{DW_AT_type :${int_label}}
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} {
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DW_TAG_subrange_type {
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{DW_AT_type :$int_label}
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{DW_AT_upper_bound 0 DW_FORM_data1}
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}
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}
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varval3_def_label: DW_TAG_variable {
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{DW_AT_name "varval3"}
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{DW_AT_external 1 DW_FORM_flag}
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{DW_AT_type :${int_array_of_1_label}}
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{DW_AT_location {DW_OP_addr [gdb_target_symbol "var_a"]} SPECIAL_expr}
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}
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DW_TAG_subprogram {
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{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
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{DW_AT_type :${int_label}}
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@ -277,19 +304,24 @@ proc setup_exec { arg_bad } {
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if [prepare_for_testing "failed to prepare" ${executable} [list ${asm_file} ${srcfile}] {}] {
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return -1
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}
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# DW_OP_GNU_variable_value implementation requires a valid frame.
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if ![runto_main] {
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return -1
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}
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}
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if { [setup_exec 0] == -1 } {
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return -1
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}
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with_test_prefix "pre-main" {
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gdb_test "print varval3" "= \\{8\\}" ""
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}
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# DW_OP_GNU_variable_value implementation requires a valid frame.
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if ![runto_main] {
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return -1
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}
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gdb_test "print varval" "= 8"
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gdb_test "print varval2" "= 8"
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gdb_test "print varval3" "= \\{8\\}"
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gdb_test "print constval" "= 53"
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gdb_test "print mixedval" "= 42"
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gdb_test "print pointerval" "= \\(int \\*\\) $hex <var_b>"
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@ -311,6 +343,10 @@ if { [setup_exec 1] == -1 } {
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return -1
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}
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# DW_OP_GNU_variable_value implementation requires a valid frame.
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if ![runto_main] {
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return -1
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}
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gdb_test "print badval" "value has been optimized out"
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gdb_test "print bad_die_val1" \
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"invalid dwarf2 offset 0xabcdef11"
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