[Boost-users] boost::format warning

Subject: [Boost-users] boost::format warning
From: Henning Meyer (tutmann_at_[hidden])
Date: 2010-01-15 15:35:45

Hello,

when compiling a simple test like this:

#include <boost/format.hpp>
int main(void) {
int c = 0;
boost::format("%1% %2%") % (c==42) % c++;
}

with this command:
$ c++ -c -O -Wall -o ftest.o ftest.cc

I get this warning:
ftest.cc: In function ‘int main()’:
ftest.cc:4: warning: operation on ‘c’ may be undefined

What did I do wrong?

Thanks for the help!

Henning

$ c++ -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
4.4.1-4ubuntu8' --with-bugurl=file:///usr/share/doc/gcc-4.4/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 --with-gxx-include-dir=/usr/include/c++/4.4
--program-suffix=-4.4 --enable-nls --enable-clocale=gnu
--enable-libstdcxx-debug --enable-objc-gc --enable-targets=all
--disable-werror --with-arch-32=i486 --with-tune=generic
--enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu
--target=i486-linux-gnu
Thread model: posix
gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu8)

$ uname -a
Linux treponema 2.6.31-17-generic #54-Ubuntu SMP Thu Dec 10 16:20:31 UTC
2009 i686 GNU/Linux