libm

I have a problem during try to compile sources with recent android-9 x86 platform. Primary question: why static library libm.a and dynamic libm.so are different? Problem is i've try to compile: /path/to/android-ndk-r8/toolchains/x86-4.4.3/prebuilt/linux-x86/bin/i686-android-linux-gcc --sysroot=/path/to/android-ndk-r8/platforms/android-9/arch-x86 -I/path/to/android-ndk-r8/sources/cxx-stl/gnu-libstdc++/include -I/path/to/android-ndk-r8/sources/cxx-stl/gnu-libstdc++/libs/x86/include -L/path/to/android-ndk-r8/sources/cxx-stl/gnu-libstdc++/lib -L/path/to/android-ndk-r8/platforms/android-9/arch-x86

With some compilers, using pow and certain other functions in a C program requires linking to the m library . However, some compilers don't require this and would error out on linking to the m library. An almost identical situation exists for C++ with std::thread and pthread , but the CMake module FindThreads alleviates this entirely - is there some similar module for libm? What is the best way to detect what to do with CMake? This is my current solution, which is less than ideal because there are many more C compilers than just GCC and MSVC: if(NOT MSVC) target_link_libraries(my-c-target

This question already has an answer here: undefined reference to sqrt (or other mathematical functions) 5 answers I'm very new to C and I have this code: #include <stdio.h> #include <math.h> int main(void) { double x = 0.5; double result = sqrt(x); printf("The square root of %lf is %lf\n", x, result); return 0; } But when I compile this with: gcc test.c -o test I get an error like this: /tmp/cc58XvyX.o: In function `main': test.c:(.text+0x2f): undefined reference to `sqrt' collect2: ld returned 1 exit status Why does this happen? Is sqrt() not in the math.h header file? I get the same error