https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98070
Bug ID: 98070
Summary: errno is not re-evaluated after clearing errno and
calling realloc(ptr, SIZE_MAX)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: stli at linux dot ibm.com
Target Milestone: ---
Created attachment 49652
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49652&action=edit
Testcase reproducing the issue with gcc-head
Hi,
After setting errno=0 and calling realloc with a too large size, which sets
errno to ENOMEM, a subsequent "if (errno == ENOMEM)" is not evaluated as true.
Instead gcc assumes that errno has not changed and is directly executing the
else-path without testing errno again.
This happens in the glibc-testcase:
<glibc>/malloc/tst-malloc-too-large.c test
(see
https://sourceware.org/git/?p=glibc.git;a=blob;f=malloc/tst-malloc-too-large.c;h=b5ad7eb7e7bf764fe57ceff5a810e3c211ca05e0;hb=refs/heads/master)
on at least x86_64 and s390x with gcc-head.
The attached small reproducer fails with gcc-head, but not with gcc 10, 9
(before):
/* Output with gcc 11:
$ ./tst-errno-realloc (build with >= -O1)
47: errno == 0 (Cannot allocate memory). We are in the else-part of 'if
(errno == ENOMEM)'. Does errno correspond to %m or the line below or to '(gdb)
p errno'?!
dump_errno(48, compare to line above!): errno == 12 (Cannot allocate memory)
vs main_errno=0
On s390x:
$ gcc -v
Using built-in specs.
COLLECT_GCC=./install-s390x-head/bin/gcc
COLLECT_LTO_WRAPPER=/home/stli/gccDir/install-s390x-head/libexec/gcc/s390x-ibm-linux-gnu/11.0.0/lto-wrapper
Target: s390x-ibm-linux-gnu
Configured with: /home/stli/gccDir/gcc-head/configure
--prefix=/home/stli/gccDir/install-s390x-head/ --enable-shared
--with-system-zlib --enable-threads=posix --enable-__cxa_atexit
--enable-checking --enable-gnu-indirect-function --enable-languages=c,c++
--with-arch=zEC12 --with-tune=z13 --disable-bootstrap --with-long-double-128
--enable-decimal-float
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.0 20201127 (experimental) (GCC)
$ git log --oneline
5e9f814d754 (HEAD -> master, origin/master, origin/HEAD) rs6000: Change
rs6000_expand_vector_set param
Also on x86_64:
$ gcc -v
Using built-in specs.
COLLECT_GCC=/home/stli/gccDir/install-x86_64-head/bin/gcc
COLLECT_LTO_WRAPPER=/home/stli/gccDir/install-x86_64-head/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /home/stli/gccDir/gcc-head/configure
--prefix=/home/stli/gccDir/install-x86_64-head/ --enable-shared
--with-system-zlib --enable-threads=posix --enable-__cxa_atexit
--enable-checking --enable-gnu-indirect-function --enable-languages=c,c++
--with-tune=generic --with-arch_32=x86-64 --disable-bootstrap
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array --disable-libgcj --disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.0.0 20201130 (experimental) (GCC)
$ git log --oneline
a5ad5d5c478 (HEAD -> master, origin/master, origin/HEAD) RISC-V: Always
define MULTILIB_DEFAULTS
*/
