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Hi,<br>
<br>
it is an interesting problem. If you tell the gcc to use the math
library, it works. The interesting thing is the way of testing.<br>
<br>
The cmake macro simply declares a function foo with the signature<br>
char foo();<br>
and call this one without arguments. If you tell cmake to link against
the math library, it works.<br>
<br>
But, if you simply call sqrt(5.0) the library is ommitted (I think the
gcc optimizes the code?)<br>
<br>
So, if you always know the math library for the specific platform, you
should use it.<br>
<br>
Hth,<br>
<br>
Andreas<br>
<br>
Am 19.09.2012 17:08, schrieb Jack Stalnaker:
<blockquote
cite="mid:CAOGUJ6HQ_fcJiV1Re7sJoKQezcXk=e4pxv6e9cidmueSEBkfWg@mail.gmail.com"
type="cite">Hi,
<div><br>
</div>
<div>I'm having trouble with check_function_exists() when it comes to
built-in functions in gcc. If I create just a simple C++ file with a
call to sqrt() or pow() and have a CMakeLists.txt with the following
lines,</div>
<div><br>
</div>
<div>include (CheckFunctionExists)</div>
<div>check_function_exists(sqrt HAVE_SQRT)</div>
<div><br>
</div>
<div>cmake fails to find sqrt (or pow, log, exp, etc). In the sqrt
case, CMakeError.log shows </div>
<div><br>
</div>
<div>/usr/share/cmake/Modules/CheckFunctionExists.c:3: warning:
conflicting types for built-in function 'sqrt'</div>
<div>Linking C executable cmTryCompileExec</div>
<div>/usr/bin/cmake -E cmake_link_script
CMakeFiles/cmTryCompileExec.dir/link.txt --verbose=1</div>
<div>/usr/bin/gcc -DCHECK_FUNCTION_EXISTS=sqrt -fPIC
CMakeFiles/cmTryCompileExec.dir/CheckFunctionExists.c.o -o
cmTryCompileExec -rdynamic </div>
<div>CMakeFiles/cmTryCompileExec.dir/CheckFunctionExists.c.o: In
function 'main': </div>
<div>CheckFunctionExists.c:(.text+0x15): undefined reference to 'sqrt'</div>
<div><br>
</div>
<div>What is the workaround for this, in the situation where the
function is built in, but I want to test for it on other platforms?</div>
<div><br>
</div>
<div>Thanks</div>
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