Problem with GCC

Hello community,

I know this is not an algorithms related question, but, I was just testing some C programs for university here and found out that somehow my C compiler does NOT recognizes any functions included in the #include <math.h> header.

Even when I attempt to compile with -lm compiler flag to link the code against the math library it gives me an error of “undefined reference to sqrt, pow”…

I am running Ubuntu 12.10 and here is the result of my gcc -v command:

 gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.7.2-2ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs --enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.7 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1)

I have checked gcc wiki and Ubuntu forums and got nowhere… Also, the same code compiled on IDEONE runs perfectly… Any help would be highly appreciated :slight_smile:

Thanks in advance,


what is the exact command you are using to compile this program ?

gcc -lm -o estruturas structs_1.c

where structs_1.c is the source file…

Compile your program like this :

gcc -o estruturas structs_1.c -lm

NOTE that you need to put -lm flag in the end of the command. In newer versions of gcc the linker flag need to be placed in the end.


Correct :slight_smile:

Thank you very much ron2794,

This was exactly what I needed :smiley: Now all is working properly

Best regards,

Bruno Oliveira