https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66422
Bug ID: 66422
Summary: -Warray-bounds false positive with -O3
Product: gcc
Version: 5.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: gajjanagadde at gmail dot com
Target Milestone: ---
Created attachment 35698
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35698&action=edit
test
Compiling the following code on GCC 5.1.0 produces a bogus out of bounds
warning:
-------
#include <inttypes.h>
// Simple test file to trigger this bug
// Two things noticed:
// 1. commenting out const char* bar results in no warning
// 2. Changing the "loop" in run_foo to a single, direct control
// results in no warning
// (These were done independently of each other, starting with this file)
typedef struct foo {
uint8_t foo_size;
int buf[4];
const char* bar;
} foo;
const foo *get_foo(int index);
static int foo_loop(const foo *myfoo) {
int i;
if (myfoo->foo_size < 3)
return 0;
for (i = 0; i < myfoo->foo_size; i++) {
if (myfoo->buf[i] != 1)
return 0;
}
return 1;
}
static int run_foo(void) {
int i;
for (i = 0; i < 1; i++) {
const foo *myfoo = get_foo(i);
if (foo_loop(myfoo))
return 0;
}
return -1;
}
// To suppress "unused run_foo" warning
typedef struct hack {
int (*func)(void);
} hack;
hack myhack = {
.func = run_foo,
};
----------------------
%gcc -Warray-bounds -O3 -c test.c
test.c: In function ‘run_foo’:
test.c:22:23: warning: array subscript is above array bounds [-Warray-bounds]
if (myfoo->buf[i] != 1)
-----------------------
config:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/5.1.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /build/gcc/src/gcc-5-20150519/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --disable-multilib --disable-werror
--enable-checking=release --with-default-libstdcxx-abi=c++98
Thread model: posix
gcc version 5.1.0 (GCC)
