Customizing the compilation process

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The Passenger compilation process can be customized with environment variables. You can learn more about environment variables in About environment variables.

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Setting the compiler

You can force the Passenger build system to use a specific C or C++ compiler by setting the CC and CXX environment variables. These may be set to any arbitrary shell commands.

For example, contributors who want to hack on Passenger may want to use Clang for faster compilation and ccache for faster recompilation, and may want to enable more error-catching compilation flags:

export CC='ccache clang -fcolor-diagnostics -Qunused-arguments -fcatch-undefined-behavior -ftrapv'
export CXX='ccache clang++ -fcolor-diagnostics -Qunused-arguments -fcatch-undefined-behavior -ftrapv'

Adding additional compiler or linker flags

On some systems, C/C++ libraries and headers that Passenger requires may be located in a non-standard directory. You can force the Passenger build system to look in those locations by injecting compiler and linker flags using the following environment variables:

EXTRA_PRE_CFLAGS

These flags are injected into all C compiler invocations that involve compiling C source files. This also covers compiler invocations that compile and link. The flags are injected at the beginning of the command string, even before EXTRA_PRE_LDFLAGS.

EXTRA_CFLAGS

Similar to EXTRA_PRE_CFLAGS, but injected at the end of the command string, before EXTRA_LDFLAGS.

EXTRA_PRE_CXXFLAGS

Similar to EXTRA_PRE_CFLAGS, but for C++ compiler invocations.

EXTRA_CXXFLAGS

Similar to EXTRA_CFLAGS, but for C++ compiler invocations.

EXTRA_PRE_LDFLAGS

These flags are injected into all C/C++ compiler invocations that involve linking. This includes compiler invocations that compile and link. The flags are injected at the beginning of the command string, but after EXTRA_PRE_CFLAGS/EXTRA_PRE_CXXFLAGS.

EXTRA_PRE_C_LDFLAGS

These flags are injected into all C compiler invocations that involve linking, right after EXTRA_PRE_LDFLAGS.

EXTRA_PRE_CXX_LDFLAGS

Similar to EXTRA_PRE_CXX_LDFLAGS, but for C++ compiler invocations.

EXTRA_LDFLAGS

Similar to EXTRA_PRE_LDFLAGS, but injected at the very end of the command string, even after EXTRA_CFLAGS and EXTRA_CXXFLAGS.

EXTRA_C_LDFLAGS

Similar to EXTRA_LDFLAGS, but only injected for C executable linking commands. Injected right after EXTRA_LDFLAGS.

EXTRA_CXX_LDFLAGS

Similar to EXTRA_LDFLAGS, but only injected for C++ executable linking commands. Injected right after EXTRA_LDFLAGS.

PASSENGER_THREAD_LOCAL_STORAGE

Setting this to 1 will enable the PASSENGER_THREAD_LOCAL_STORAGE macro, which forcefully disables the use of thread-local storage inside the Passenger codebase. Setting this environment variable is useful on systems that have broken support for thread-local storage, despite passing our build system's check for proper thread-local storage support. At the time of writing, one user has reported that Ubuntu 12.04 32-bit has broken thread-local storage report although neither the reporter nor us were able to reproduce the problem on any other systems running Ubuntu 12.04 32-bit. Note that this flag has no effect on non-Passenger code.

Forcing location of command line tools and dependencies

The Passenger build system attempts to autodetect many things by locating relevant helper tools. For example, to find out which compiler flags it should use for libcurl, it queries the curl-config command. These commands may not be in $PATH, or even when they are you may want to use a different one.

You can force the build to find certain command line tools at certain locations by using the following environment variables:

MAKE

The location of a make tool. It does not matter which implementation of make this is.

GMAKE

The location of the GNU-compatible make tool.