https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105013
Bug ID: 105013
Summary: Valgrind reports accessing uninitialized memory when
-O2 option is used
Product: gcc
Version: 9.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jamesallwright at yahoo dot co.uk
Target Milestone: ---
Created attachment 52660
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52660&action=edit
bug.i generated by gcc
When the below code is compiled using the -O2 option, valgrind reports
"Conditional jump or move depends on uninitialised value(s)".
This does not happen if -O2 is not used.
#include <stdio.h>
#include <string.h>
#include <ctype.h>
void
readstr (char out[], char **in, int limit)
{
int i;
i = 0;
while ((isalpha (**in)) && (i < limit - 1))
{
out[i] = **in;
i = i + 1;
*in = *in + 1;
};
out[i] = '\0';
printf("out = %s\n", out);
if (strcmp(out, "channel") == 0) {
printf("channel\n");
}
}
void example_func(char *s)
{
char command[40];
char *p;
p = s;
readstr(command, &p, 40);
printf("command = %s\n", command);
/* line below generates valgrind warning
* Conditional jump or move depends on uninitialised value(s)
*/
if (strcmp(command, "channel") == 0) {
printf("channel\n");
}
}
int main(int argc, char **argv)
{
example_func("%%sausage 1 2");
}
As requested in your bug submission notes, I ran gcc with data collextion
options:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/9/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
9.4.0-1ubuntu1~20.04' --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,gm2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-9
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new
--enable-gnu-unique-object --disable-vtable-verify --enable-plugin
--enable-default-pie --with-system-zlib --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-9-yTrUTS/gcc-9-9.4.0/debian/tmp-nvptx/usr,hsa
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04)
I am also attaching bug.i generated by this command
