https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86873
Bug ID: 86873
Summary: "gcc -lmcheck" aborts on free when using
posix_memalign
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ben at tawesoft dot co.uk
Target Milestone: ---
Created attachment 44513
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44513&action=edit
Minimal example (.i version)
Simple C programs using `posix_memalign()` and `free()`, compiled with `gcc
-lmcheck`, cause the resulting binary to raise a runtime error such as
`munmap_chunk(): invalid pointer`.
For example,
#include <stdlib.h>
#include <stdio.h>
int main()
{
void *p = 0;
int ret = posix_memalign(&p, sizeof(void*), 0);
printf("ret was %d, pointer is %p\n", ret, p);
free(p);
return 0;
}
The full example including headers is attached.
Note that "POSIX requires that memory obtained from posix_memalign() can be
freed using free".
Output (my system):
$ gcc test.c -lmcheck -ggdb
$ ./a.out
ret was 0, pointer is 0xcb6090
*** Error in `./a.out': munmap_chunk(): invalid pointer: 0x0000000000cb6060
***
Aborted
Output (NVIDIA developer):
$ gcc test.c -lmcheck -ggdb
$ ./a.out
ret was 0, pointer is 0x558c32d102e0
munmap_chunk(): invalid pointer
Aborted (core dumped)
Expected output:
$ gcc test.c -lmcheck -ggdb
$ ./a.out
ret was 0, pointer is 0x<some-address>
This was initially discovered due to posix_memalign's use in the Nvidia
graphics driver -- discussion here, three people report same symptoms:
https://devtalk.nvidia.com/default/topic/1037171/linux/memory-error-in-glx-programs-when-linked-with-gcc-lmcheck/
For me, here is the GCC version that raises this. I am aware this is an old
version of GCC as provided by what is currently Debian odstable (Jessie), but
others have reported the same results.
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian
4.9.2-10+deb8u1' --with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-10+deb8u1)
Obviously, I am using an old version of GCC but I hope this bug report may be
of use to anyone using a search engine to lookup a problem with this possible
lmcheck false positive.
