From: Eric Botcazou <botcazou@adacore.com>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH] Fix bogus -Wstringop-overflow warning
Date: Thu, 13 Oct 2022 14:06:15 +0200 [thread overview]
Message-ID: <3194055.aeNJFYEL58@fomalhaut> (raw)
[-- Attachment #1: Type: text/plain, Size: 1315 bytes --]
Hi,
if you compile the attached testcase with -O2 -fno-inline -Wall, you get:
In function 'process_array3':
cc1: warning: 'process_array4' accessing 4 bytes in a region of size 3 [-
Wstringop-overflow=]
cc1: note: referencing argument 1 of type 'char[4]'
t.c:6:6: note: in a call to function 'process_array4'
6 | void process_array4 (char a[4], int n)
| ^~~~~~~~~~~~~~
cc1: warning: 'process_array4' accessing 4 bytes in a region of size 3 [-
Wstringop-overflow=]
cc1: note: referencing argument 1 of type 'char[4]'
t.c:6:6: note: in a call to function 'process_array4'
That's because the ICF IPA pass has identified the two functions and turned
process_array3 into a wrapper of process_array4. This looks sensible to me
given that the only difference between them is an "access" attribute on their
type describing the access size of the parameter and the "access" attribute
does not affect type identity (struct attribute_spec.affects_type_identity).
Hence the proposed fix, tested on x86-64/Linux, OK for the mainline?
2022-10-13 Eric Botcazou <ebotcazou@adacore.com>
* gimple-ssa-warn-access.cc (pass_waccess::check_call): Return
early for calls made from thunks.
2022-10-13 Eric Botcazou <ebotcazou@adacore.com>
* gcc.dg/Wstringop-overflow-89.c: New test.
--
Eric Botcazou
[-- Attachment #2: p.diff --]
[-- Type: text/x-patch, Size: 862 bytes --]
diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index 04aa849a4b1..59a70530600 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -4291,14 +4291,18 @@ pass_waccess::check_pointer_uses (gimple *stmt, tree ptr,
void
pass_waccess::check_call (gcall *stmt)
{
- if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
- check_builtin (stmt);
+ /* Skip special calls generated by the compiler. */
+ if (gimple_call_from_thunk_p (stmt))
+ return;
/* .ASAN_MARK doesn't access any vars, only modifies shadow memory. */
if (gimple_call_internal_p (stmt)
&& gimple_call_internal_fn (stmt) == IFN_ASAN_MARK)
return;
+ if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
+ check_builtin (stmt);
+
if (!m_early_checks_p)
if (tree callee = gimple_call_fndecl (stmt))
{
[-- Attachment #3: Wstringop-overflow-89.c --]
[-- Type: text/x-csrc, Size: 286 bytes --]
/* { dg-do compile } */
/* { dg-options "-O2 -fno-inline -Wall" } */
extern void process (char);
void process_array4 (char a[4], int n)
{
for (int i = 0; i < n; i++)
process (a[i]);
}
void process_array3 (char a[3], int n)
{
for (int i = 0; i < n; i++)
process (a[i]);
}
next reply other threads:[~2022-10-13 12:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 12:06 Eric Botcazou [this message]
2022-10-13 22:31 ` Jeff Law
2022-10-13 22:53 ` Eric Botcazou
2022-10-14 6:12 ` Richard Biener
2022-10-14 10:27 ` Martin Liška
2022-10-14 11:59 ` Martin Jambor
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