https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65194
Bug ID: 65194
Summary: Compiler warns of maybe-uninitialized
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jengelh at inai dot de
Created attachment 34857
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34857&action=edit
A testcase. (It used to be over 60000 lines after the initial g++ -E, so excuse
if I did not resolve #include <string>)
The attached testcase warns of maybe-used uninitialized.
> g++-4.9 m.cpp -Wall -O2 -ggdb3 -o m -std=gnu++11
m.cpp: In function ‘int main()’:
m.cpp:25:13: warning: ‘idx’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
srand(idx);
^
However, as soon as one modifies the source, the warning disappears. Pick one
of the transformations from the bullet point list, and it goes away.
* replace *one* instance of "new char" by "NULL"
* replace "new str" by "new char"
* replace "std::string" by "str"
This happens both with
Using built-in specs.
COLLECT_GCC=g++-4.9
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/4.9/lto-wrapper
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada,go
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.9
--enable-ssp --disable-libssp --disable-libvtv --disable-plugin
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--disable-libgcj --with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --enable-linker-build-id
--enable-linux-futex --program-suffix=-4.9 --without-system-libunwind
--enable-multilib --with-arch-32=i586 --with-tune=generic
--build=x86_64-suse-linux --host=x86_64-suse-linux
Thread model: posix
gcc version 4.9.0 (SUSE Linux)
and
Using built-in specs.
COLLECT_GCC=g++-4.8
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/4.8/lto-wrapper
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.8
--enable-ssp --disable-libssp --disable-plugin
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--disable-libgcj --disable-libmudflap --with-slibdir=/lib64 --with-system-zlib
--enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --enable-linker-build-id
--enable-linux-futex --program-suffix=-4.8 --without-system-libunwind
--with-arch-32=i586 --with-tune=generic --build=x86_64-suse-linux
--host=x86_64-suse-linux
Thread model: posix
gcc version 4.8.3 20140627 [gcc-4_8-branch revision 212064] (SUSE Linux)
What might be happening in gcc?
