Well that's strange. I've tested on the following Perls:
- Windows Vista Home Premium 64 bit / Strawberry Perl version 5.12.3
- Ubuntu Linux 32 bit version 11.10 / System Perl version 5.12.4
- Ubuntu Linux 32 bit version 11.10 / Perlbrew-managed Perl version 5.14.2
Is it possible that your Inline::C is installed using a different compiler from the one used to compile Perl? That can make a difference. When I installed using cpan Inline::C, I was prompted for which compiler to use, but the default had already detected the compiler used to compile Perl, so I just accepted the default.
Test::More is used by just about every module you install, so I would be more inclined to put the blame on Inline::C than on Test::More.