The math library must be linked in when building the executable. How to do this varies by environment, but in Linux/Unix, just add -lm to the command: gcc test.c -o test -lm The math library is named libm.so, and the -l command option assumes a lib prefix and .a or .so suffix.
Statically linking against any system library, and especially against libc, on modern UNIX or Linux systems makes the binary significantly less portable. Just don’t do it. Instead, use backward compatibility (binaries linked on an older system continue to run on all newer ones) to your advantage, either by linking your binary on an old system … Read more
The R_X86_64_32S and R_X86_64_64 are names of relocation types, for code compiled for the amd64 architecture. You can look all of them up in the amd64 ABI. According to it, R_X86_64_64 is broken down to: R_X86_64 – all names are prefixed with this 64 – Direct 64 bit relocation and R_X86_64_32S to: R_X86_64 – prefix … Read more
The problem is the linker is looking for libmagic.so but you only have libmagic.so.1 A quick hack is to symlink libmagic.so.1 to libmagic.so
An object file is the real output from the compilation phase. It’s mostly machine code, but has info that allows a linker to see what symbols are in it as well as symbols it requires in order to work. (For reference, “symbols” are basically names of global objects, functions, etc.) A linker takes all these … Read more
You can do this by executing the following command: ld –verbose | grep SEARCH_DIR | tr -s ‘ ;’ \\012 gcc passes a few extra -L paths to the linker, which you can list with the following command: gcc -print-search-dirs | sed ‘/^lib/b 1;d;:1;s,/[^/.][^/]*/\.\./,/,;t 1;s,:[^=]*=,:;,;s,;,; ,g’ | tr \; \\012 The answers suggesting to use … Read more
It is used in the stack unwiding tables, which you can see for instance in the assembly output of my answer to another question. As mentioned on that answer, its use is defined by the Itanium C++ ABI, where it is called the Personality Routine. The reason it “works” by defining it as a global … Read more
Which combinations of these objects is it and isn’t it safe to link into a single binary? Why? For GCC it is safe to link together any combination of objects A, B, and C. If they are all built with the same version then they are ABI compatible, the standard version (i.e. the -std option) … Read more
The link command line is set in Modules/CMake{C,CXX,Fortran}Information.cmake and defaults to using the compiler, not CMAKE_LINKER (see source code). This can be changed by replacing the rule that builds the link command line, which lives in variables CMAKE_CXX_LINK_EXECUTABLE (and friends). NB that variable does not indicate the path to the linker executable; it says how … Read more
In addition to the support for Link Time Code Generation (LTCG) that Jame McNellis mentioned, the GCC toolchain also supports link time optimization. Starting with version 4.5, GCC supports the -flto switch which enables Link Time Optimization (LTO), a form of whole program optimization that lets it inline functions from separate object files (and whatever … Read more