PR analyzer/104308 reports that when -Wanalyzer-use-of-uninitialized-value
complains about certain memmove operations where the source is
uninitialized, the diagnostic uses UNKNOWN_LOCATION:
In function 'main':
cc1: warning: use of uninitialized value '*(short unsigned int *)&s + 1'
[CWE-457] [-Wanalyzer-use-of-uninitialized-value]
'main': event 1
|
|pr104308.c:5:8:
| 5 | char s[5]; /* { dg-message "region created on stack here" } */
| | ^
| | |
| | (1) region created on stack here
|
'main': event 2
|
|cc1:
| (2): use of uninitialized value '*(short unsigned int *)&s + 1' here
|
The issue is that gimple_fold_builtin_memory_op converts a memmove to:
_3 = MEM <unsigned short> [(char * {ref-all})_1];
MEM <unsigned short> [(char * {ref-all})&s] = _3;
but only sets the location of the 2nd stmt, not the 1st.
Fixed thusly, giving:
pr104308.c: In function 'main':
pr104308.c:6:3: warning: use of uninitialized value '*(short unsigned int *)&s
+ 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" }
*/
| ^~~~~~~~~~~~~~~~~~~~
'main': events 1-2
|
| 5 | char s[5]; /* { dg-message "region created on stack here" } */
| | ^
| | |
| | (1) region created on stack here
| 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized
value" } */
| | ~~~~~~~~~~~~~~~~~~~~
| | |
| | (2) use of uninitialized value '*(short unsigned int *)&s + 1'
here
|
One side-effect of this change is a change in part of the output of
gcc.dg/uninit-40.c from:
uninit-40.c:47:3: warning: ‘*(long unsigned int *)(&u[1][0][0])’ is used
uninitialized [-Wuninitialized]
47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
uninit-40.c:45:5: note: ‘*(long unsigned int *)(&u[1][0][0])’ was declared
here
45 | V u[2], v[2];
| ^
to:
uninit-40.c:47:3: warning: ‘u’ is used uninitialized [-Wuninitialized]
47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
uninit-40.c:45:5: note: ‘u’ declared here
45 | V u[2], v[2];
| ^
What's happening is that pass "early_uninit"(29)'s call to
maybe_warn_operand is guarded by this condition:
1051 else if (gimple_assign_load_p (stmt)
1052 && gimple_has_location (stmt))
Before the patch, the stmt:
_3 = MEM <unsigned long> [(char * {ref-all})&u + 8B];
has no location, and so early_uninit skips this operand at line
1052 above. Later, pass "uninit"(217) tests the var_decl "u$8", and
emits a warning for it.
With the patch, the stmt has a location, and so early_uninit emits a
warning for "u" and sets a NW_UNINIT warning suppression at that
location. Later, pass "uninit"(217)'s test of "u$8" is rejected
due to that per-location suppression of uninit warnings, from the
earlier warning.
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
OK for stage 4? or for next stage 1?
gcc/ChangeLog:
PR analyzer/104308
* gimple-fold.cc (gimple_fold_builtin_memory_op): When optimizing
to loads then stores, set the location of the new load stmt.
gcc/testsuite/ChangeLog:
PR analyzer/104308
* gcc.dg/analyzer/pr104308.c: New test.
* gcc.dg/uninit-40.c (foo): Update expression in expected message.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
gcc/gimple-fold.cc | 1 +
gcc/testsuite/gcc.dg/analyzer/pr104308.c | 8 ++++++++
gcc/testsuite/gcc.dg/uninit-40.c | 2 +-
3 files changed, 10 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr104308.c
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 5eff7d68ac1..e73bc6a7137 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -1039,6 +1039,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
new_stmt);
gimple_assign_set_lhs (new_stmt, srcmem);
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+ gimple_set_location (new_stmt, loc);
gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
}
if (dest_align < GET_MODE_ALIGNMENT (mode))
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c
b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
new file mode 100644
index 00000000000..9cd5ee6feee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
@@ -0,0 +1,8 @@
+#include <string.h>
+
+int main()
+{
+ char s[5]; /* { dg-message "region created on stack here" } */
+ memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-40.c b/gcc/testsuite/gcc.dg/uninit-40.c
index 8708079d397..567707a885e 100644
--- a/gcc/testsuite/gcc.dg/uninit-40.c
+++ b/gcc/testsuite/gcc.dg/uninit-40.c
@@ -44,7 +44,7 @@ foo (int *q)
/* memcpy folding is too target dependent to test it everywhere. */
V u[2], v[2];
u[0][0][0] = 1;
- __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning
"'\\*\\(\(long \)?long unsigned int \\*\\)\\(&u\\\[1\\\]\\\[0\\\]\\\[0\\\]\\)'
is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
+ __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'u' is
used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
baz (&v[1]);
#endif
}
--
2.26.3
