4.3 Environment variables ¶

When running client code against a locally-built libgccjit, three environment variables need to be set up:

Environment Variable: LD_LIBRARY_PATH ¶

libgccjit.so is dynamically linked into client code, so if running against a locally-built library, LD_LIBRARY_PATH needs to be set up appropriately. The library can be found within the “gcc” subdirectory of the build tree:

$ file libgccjit.so*
libgccjit.so:       symbolic link to `libgccjit.so.0'
libgccjit.so.0:     symbolic link to `libgccjit.so.0.0.1'
libgccjit.so.0.0.1: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, not stripped

Environment Variable: PATH ¶

The library uses a driver executable for converting from .s assembler files to .so shared libraries. Specifically, it looks for a name expanded from ${target_noncanonical}-gcc-${gcc_BASEVER}${exeext} such as x86_64-unknown-linux-gnu-gcc-5.0.0.

Hence PATH needs to include a directory where the library can locate this executable.

The executable is normally installed to the installation bindir (e.g. /usr/bin), but a copy is also created within the “gcc” subdirectory of the build tree for running the testsuite, and for ease of development.

Environment Variable: LIBRARY_PATH ¶

The driver executable invokes the linker, and the latter needs to locate support libraries needed by the generated code, or you will see errors like:

ld: cannot find crtbeginS.o: No such file or directory
ld: cannot find -lgcc
ld: cannot find -lgcc_s

Hence if running directly from a locally-built copy (without installing), LIBRARY_PATH needs to contain the “gcc” subdirectory of the build tree.

For example, to run a binary that uses the library against a non-installed build of the library in LIBGCCJIT_BUILD_DIR you need an invocation of the client code like this, to preprend the dir to each of the environment variables:

$ LD_LIBRARY_PATH=$(LIBGCCJIT_BUILD_DIR):$(LD_LIBRARY_PATH) \
  PATH=$(LIBGCCJIT_BUILD_DIR):$(PATH) \
  LIBRARY_PATH=$(LIBGCCJIT_BUILD_DIR):$(LIBRARY_PATH) \
    ./jit-hello-world
hello world