If a vla is not in memory, and the upper bound is not defined, then we
can't know that an array element exists or not, and we should not try
to access the array element. One case where this happens is for
arrays that have been optimised out, the array will then have
VALUE_LVAL of not_lval, and an undefined upper bound, if we then try
to access an element of this array we will index into random GDB
memory.
An argument could be made that even for arrays that are in inferior
memory, if the upper bound is not defined then we should not try to
access the array element, however, in some of the Fortran tests, it
seems as though we do rely indexing from a base address into an array
which has no bounds defined. In this case GDBs standard protection
for detecting unreadable target memory prevents bad thing happening.
gdb/ChangeLog:
* valarith.c (value_subscripted_rvalue): If an array is not in
memory, and we don't know the upper bound, then we can't know that
the requested element exists or not.
gdb/testsuite/ChangeLog:
* gdb.base/vla-optimized-out.exp: Add new test.
The three test scripts:
gdb/testsuite/gdb.base/vla-optimized-out.exp
gdb/testsuite/gdb.base/vla-optimized-out-o3.exp
gdb/testsuite/gdb.base/vla-optimized-out-o3-strict.exp
are all pretty similar, with differences in the compile flags used,
and some of the expected results.
Instead of maintaining 3 files, merge them into a single test script,
and use parameters to control the test behaviour.
gdb/testsuite/ChangeLog:
* gdb.base/vla-optimized-out-o3.exp: Delete.
* gdb.base/vla-optimized-out-o3-strict.exp: Delete.
* gdb.base/vla-optimized-out.exp: Extend to cover all of the
deleted tests.
Make the noclone attribute on f1 in vla-optimized-out.c conditional. This
makes the test-case by default identical to
gcc/testsuite/gcc.dg/guality/vla-1.c.
Tested on x86_64-linux.
2018-07-20 Tom de Vries <tdevries@suse.de>
* gdb.base/vla-optimized-out.c: Make noclone attribute conditional on
NOCLONE macro.
* gdb.base/vla-optimized-out.exp: Use additional_flags -DNOCLONE.
Consider this snippet from gcc/testsuite/gcc.dg/guality/vla-1.c:
...
int __attribute__((noinline))
f1 (int i)
{
char a[i + 1];
a[0] = 5; /* { dg-final { gdb-test .+1 "i" "5" } } */
return a[0]; /* { dg-final { gdb-test . "sizeof (a)" "6" } } */
}
...
When we compile the test-case with -O1 -g, and query the size of optimized
out vla 'a', we get:
...
$ ./gdb -batch -ex "b f1" -ex "r" -ex "p sizeof (a)" vla-1.exe
Breakpoint 1 at 0x4004a8: file vla-1.c, line 17.
Breakpoint 1, f1 (i=i@entry=5) at vla-1.c:17
17 return a[0];
$1 = 0
...
while we expect a size of '6'.
The problem is that default_read_var_value does not resolve the dynamic type
of a variable if the variable is optimized out.
This patch fixes that, and consequently gdb prints '6', as expected.
Tested on x86_64-linux.
2018-07-18 Tom de Vries <tdevries@suse.de>
* findvar.c (default_read_var_value): Also resolve dynamic type for
LOC_OPTIMIZED_OUT vars.
* gdb.base/vla-optimized-out.c: New test.
* gdb.base/vla-optimized-out.exp: New file.
Andrew Burgess
Tom de Vries