GCC, '-pg' option and 'mcount' undefined

[Tim Prince]

On 1/3/2012 12:45 PM, Angelo Graziosi wrote:
> For the sake of completeness, I want to flag the following issue I have
> found on Cygwin.
>
> I have an application that doesn't build on Cygwin (gcc-4.5.3) because
> undefined reference to `_mcount' etc... I have tried to reproduce it
> with this simple example:
>
> $ cat hello.c
> #include <stdio.h>
>
> int main()
> {
> printf("Hello World\n");
> }
>
> $ gcc -c -pg hello.c
> $ gcc hello.o -o hello
> hello.o:hello.c:(.text+0xa): undefined reference to `_mcount'
> hello.o:hello.c:(.text+0xf): undefined reference to `__monstartup'
> collect2: ld returned 1 exit status
>
> If I try the same above example (and the true application) on Mac OS X
> Lion with gcc-4.5.3 or on GNU Linux distributions like Fedora14 (gcc
> 4.5.1), Kubuntu (gcc-4.6.1), Ubuntu (i386, gcc-4.6.1), it works just fine,
>
> $ ./hello
> Hello World
>
> If I want to build the above example on Cygwin, I need to link using the
> same option '-pg',
>
> $ gcc -pg hello.o -o hello
> $ ./hello
> Hello World
>
> Yes, I can patch my true application to use '-pg' option when it needs,
> but I would know if you (Dave?) have other ideas here.
>
It's entirely normal to require the -pg option for linking pg 
compilations.  You may even get a version of some libraries with pg 
profiling enabled.


-- 
Tim Prince

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