https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96739
Bug ID: 96739
Summary: attribute(constructor) vs format NULL check
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dgilbert at redhat dot com
Target Milestone: ---
Created attachment 49096
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49096&action=edit
boiled down test file
The following is boiled down (too far?) from current
(d6f83a72a7db94a3ede9f5cc4fb39f9c8e89f954) qemu-io-cmds.c
and generates the warning:
ioprob.c:28:5: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
28 | printf("%s ", ct->name);
| ^~~~~~~~~~~~~~~~~~~~~~~
unless the __attribute((constructor)) is removed from init_qemuio_commands
I think the problem here is that ct comes from cmdtab which is a static and it
doesn't notice that it's initialised, and therefore decides it's NULL?
cc -O1 -Wformat -Wformat-security -c ioprob.c -Wunused
In function ‘help_oneline’,
inlined from ‘help_all’ at ioprob.c:34:5,
inlined from ‘help_f’ at ioprob.c:39:5:
ioprob.c:28:5: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
28 | printf("%s ", ct->name);
| ^~~~~~~~~~~~~~~~~~~~~~~
[dgilbert@dgilbert-t580 try]$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/10/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,lto --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array --with-isl --enable-offload-targets=nvptx-none
--without-cuda-driver --enable-gnu-indirect-function --enable-cet
--with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.2.1 20200723 (Red Hat 10.2.1-1) (GCC)
