http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028
Summary: Ternary operator and static const member variable
Product: gcc
Version: 4.6.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: protocolo...@gmail.com
Created attachment 24960
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24960
Preprocessor intermediate file
Problem:
The following code:
#include <stdlib.h>
#include <stdio.h>
class test
{
public:
static const unsigned char OPT1=27;
static const unsigned char OPT2=72;
};
int main()
{
unsigned cond=rand();
unsigned value1, value2;
if(cond) value1=test::OPT1; else value1=test::OPT2;
value2=cond?test::OPT1:test::OPT2;
printf("%d %d\n", value1, value2);
return 0;
}
Compiles w/o warnings with:
$ g++ -Wall -Wextra -o testO2 -g -O2 test.cc
But fails to compile/link with:
$ g++ -Wall -Wextra -o testO2 -g -O0 test.cc
/tmp/ccwLVGVv.o: In function `main':
/home/asier/desarrollo/tmp/gcc_poc/test.cc:16: undefined reference to
`test::OPT1'
/home/asier/desarrollo/tmp/gcc_poc/test.cc:16: undefined reference to
`test::OPT2'
collect2: ld returned 1 exit status
Analysis:
The problem only happens in the ternary operator, but not in the if statement
that precedes it. Compiler is not substituting class constants in conditional
operator so that compilation unit gets a reference to a test::OPT1 and
test::OPT2 in the .rodata section (that actually does not exist).
See attacked preprocesor output and intermediate assembly code.
Compilers tested:
GCC 4.3
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.5-4'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--enable-multiarch --enable-linker-build-id --with-system-zlib
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--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 4.3.5 (Debian 4.3.5-4)
GCC 4.4
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8'
--with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.4 --enable-shared --enable-multiarch
--enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc
--with-arch-32=i586 --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 4.4.5 (Debian 4.4.5-8)
GCC 4.6
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.1-4'
--with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-multiarch
--with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib/x86_64-linux-gnu
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib/x86_64-linux-gnu
--enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc
--with-arch-32=i586 --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 4.6.1 (Debian 4.6.1-4)
System info:
Linux frito 2.6.32-5-amd64 #1 SMP Mon Mar 7 21:35:22 UTC 2011 x86_64 GNU/Linux
