Re: Profiling a library built with libtool

[Benoit SIGOURE]

On Jul 13, 2007, at 4:39 PM, Joseph Wakeling wrote:

> I have a small library which is built using the GNU autotools.  It  
> also
> includes some executable programs which use the main library.  I would
> like to profile the performance using gprof or another tool but have
> been having trouble working out how to do so.  I tried simply  
> adding -p
> to the CFLAGS but the resulting gmon.out appeared to contain no data
> (e.g. running gprof on the executable or on the .la file resulted  
> in an
> error, "not in executable format", while running it on one of the  
> object
> files produced no information).
>
> I wonder if someone could give me a brief run-through on how to  
> profile
> the library---what options I need to place in the autotools-related
> files and when using ./configure, and how to use gprof effectively on
> the library once built.

Hello Joseph,
when using libtool, the `binary' produced in the build directory is  
in fact a wrapper shell script that does some setup and then runs the  
real binary.  This is required because your executable probably  
depends on uninstalled libraries and the script does some magic  
before running it (such as, typically, setting the LD_LIBRARY_PATH if  
you're on GNU/Linux).

If, say, I have a bin_PROGRAMS `foo' that depends on a  
lib_LTLIBRARIES `libfoo.la', this is what I have:

$ file foo libfoo.la
foo:       Bourne shell script text executable
libfoo.la: ASCII English text

The .la file is a piece of shell script that contains information  
useful to libtool.

Now the answer to your question is to ask libtool to run gprof (or  
gdb) for you:
./libtool --mode=execute gprof ./foo

Cheers,

--
Benoit Sigoure aka Tsuna
EPITA Research and Development Laboratory

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