https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120205
Bug ID: 120205
Summary: [15/16 regression] unifdef miscompiled
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: sjames at gcc dot gnu.org
CC: code at musicinmybrain dot net, lschmelting at posteo dot
com
Target Milestone: ---
I noticed this test failure some time ago, but I wrongly assumed it was always
failing (as I had never looked at the package before). My bad.
Ben Beasley of Fedora noticed this the other day and it made me take another
look (https://github.com/fanf2/unifdef/pull/19#issuecomment-2863148452).
unifdef fails tests with >= GCC 15 when built with -D_FORTIFY_SOURCE (any
level). Reducing it was a bit awkward and the reduced version is equally
awkward (use of __ctype_b_loc, reliance on fgets alias, ...).
---
unifdef.c:
```
enum { _ISspace } ;
char tline[4096];
int main_argc;
char parseline_cp;
long parseline_len;
char *__fgets_alias() __asm__("fgets");
extern __inline __attribute__((__gnu_inline__)) char *fgets(char *__s) {
long __sz = __builtin_dynamic_object_size(__s, 1);
if (__sz == -1)
return __fgets_alias();
}
int getopt();
int main(char argv) {
while (getopt(main_argc, argv) != -1)
;
__builtin_printf("foo\n");
{
for (; _ISspace;)
;
if (fgets(tline + parseline_len) == 0)
__builtin_abort();
}
}
```
$ gcc-14 -O1 -o unifdef unifdef.c && ./unifdef
foo
$ gcc-15 -O1 -o unifdef unifdef.c && ./unifdef
foo
Aborted (core dumped) ./unifdef
---
```
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/16/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-16.0.9999/work/gcc-16.0.9999/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/16
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/16/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/16/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/16/include/g++-v16
--disable-silent-rules --disable-dependency-tracking
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/16/python
--enable-libphobos --enable-objc-gc
--enable-languages=c,c++,d,objc,obj-c++,fortran,ada,cobol,m2,rust
--enable-obsolete --enable-secureplt --disable-werror --with-system-zlib
--enable-nls --without-included-gettext --disable-libunwind-exceptions
--enable-checking=yes,extra,rtl --with-bugurl=https://bugs.gentoo.org/
--with-pkgversion='Gentoo Hardened 16.0.9999 p, commit
485d5bafcc11703825cb6c3cf7ce2cdd246fb7b1' --with-gcc-major-version-only
--enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-multilib --with-multilib-list=m32,m64 --disable-fixed-point
--enable-targets=all --enable-offload-defaulted
--enable-offload-targets=nvptx-none --enable-libgomp --disable-libssp
--enable-libada --disable-cet --disable-systemtap --enable-valgrind-annotations
--disable-vtable-verify --disable-libvtv --with-zstd --with-isl
--disable-isl-version-check --enable-default-pie --enable-host-pie
--enable-host-bind-now --enable-default-ssp --disable-fixincludes
--with-gxx-libcxx-include-dir=/usr/include/c++/v1 --enable-linker-build-id
--with-build-config='bootstrap-O3 bootstrap-lto'
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.0.0 20250507 (experimental)
974b079741f902fcf4323dfcecbbffdb9f56f3bf (Gentoo Hardened 16.0.9999 p, commit
485d5bafcc11703825cb6c3cf7ce2cdd246fb7b1)
```
