https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66974
Bug ID: 66974
Summary: -Warray-bounds false positive with -O3
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gajjanagadde at gmail dot com
CC: gajjanagadde at gmail dot com
Target Milestone: ---
Created attachment 36039
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36039&action=edit
gcc_warraybounds_false.i
Compiling the following code on GCC 5.2.0 produces a bogus out of bounds
warning at -O3 level:
-------
int foo(unsigned order) {
int c[3] = {1, 2, 3};
unsigned i, j;
for (i = 1; i < order; i++) {
for (j = 0; j < i / 2; j++) {
c[j] += c[i] * c[i-j-1];
c[i-j-1] += c[i] * c[j];
}
}
return c[0];
}
----------------------
%gcc -Warray-bounds -O3 -c gcc_warraybounds_false.c
gcc_warraybounds_false.c: In function ‘foo’:
gcc_warraybounds_false.c:6:22: warning: array subscript is above array bounds
[-Warray-bounds]
c[j] += c[i] * c[i-j-1];
^
gcc_warraybounds_false.c:7:26: warning: array subscript is above array bounds
[-Warray-bounds]
c[i-j-1] += c[i] * c[j];
^
gcc_warraybounds_false.c:6:22: warning: array subscript is above array bounds
[-Warray-bounds]
c[j] += c[i] * c[i-j-1];
^
gcc_warraybounds_false.c:6:29: warning: array subscript is above array bounds
[-Warray-bounds]
c[j] += c[i] * c[i-j-1];
^
gcc_warraybounds_false.c:7:22: warning: array subscript is above array bounds
[-Warray-bounds]
c[i-j-1] += c[i] * c[j];
^
gcc_warraybounds_false.c:7:26: warning: array subscript is above array bounds
[-Warray-bounds]
c[i-j-1] += c[i] * c[j];
^
gcc_warraybounds_false.c:7:22: warning: array subscript is above array bounds
[-Warray-bounds]
c[i-j-1] += c[i] * c[j];
-----------------------
config:
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /build/gcc/src/gcc-5.2.0/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=gcc4-compatible
Thread model: posix
gcc version 5.2.0 (GCC)
