# Configuring libcork¶

#include <libcork/config.h>


Several libcork features have different implementations on different platforms. Since we want libcork to be easily embeddable into projects with a wide range of build systems, we try to autodetect which implementations to use, using only the C preprocessor and the predefined macros that are available on the current system.

This module provides a layer of indirection, with all of the preprocessor-based autodetection in one place. This module’s task is to define a collection of libcork-specific configuration macros, which all other libcork modules will use to select which implementation to use.

This design also lets you skip the autodetection, and provide values for the configuration macros directly. This is especially useful if you’re embedding libcork into another project, and already have a configure step in your build system that performs platform detection. See CORK_CONFIG_SKIP_AUTODETECT for details.

Note

The autodetection logic is almost certainly incomplete. If you need to port libcork to another platform, this is where an important chunk of edits will take place. Patches are welcome!

## Configuration macros¶

This section lists all of the macros that are defined by libcork’s autodetection logic. Other libcork modules will use the values of these macros to choose among the possible implementations.

CORK_CONFIG_VERSION_MAJOR
CORK_CONFIG_VERSION_MINOR
CORK_CONFIG_VERSION_PATCH

The libcork library version, with each part of the version number separated out into separate macros.

CORK_CONFIG_VERSION_STRING

The libcork library version, encoded as a single string.

CORK_CONFIG_REVISION

The git SHA-1 commit identifier of the libcork version that you’re using.

CORK_CONFIG_ARCH_X86
CORK_CONFIG_ARCH_X64
CORK_CONFIG_ARCH_PPC

Exactly one of these macros should be defined to 1 to indicate the architecture of the current platform. All of the other macros should be defined to 0 or left undefined. The macros correspond to the following architectures:

Macro suffix Architecture
X86 32-bit Intel (386 or greater)
X64 64-bit Intel/AMD (AMD64/EM64T, not IA-64)
PPC 32-bit PowerPC
CORK_CONFIG_HAVE_GCC_ASM

Whether the GCC inline assembler syntax is available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_GCC_ATTRIBUTES

Whether the GCC-style syntax for compiler attributes is available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_GCC_ATOMICS

Whether GCC-style atomic intrinsics are available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_GCC_INT128

Whether the GCC-style 128-bit integer types (__int128 and unsigned __int128) are available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_GCC_MODE_ATTRIBUTE

Whether GCC-style machine modes are available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_GCC_STATEMENT_EXPRS

Whether GCC-style statement expressions are available. (This doesn’t imply that the compiler is specifically GCC.) Should be defined to 0 or 1.

CORK_CONFIG_HAVE_REALLOCF

Whether this platform defines a reallocf function in stdlib.h. reallocf is a BSD extension to the standard realloc function that frees the existing pointer if a reallocation fails. If this function exists, we can use it to implement cork_realloc().

CORK_CONFIG_IS_BIG_ENDIAN
CORK_CONFIG_IS_LITTLE_ENDIAN

Whether the current system is big-endian or little-endian. Exactly one of these macros should be defined to 1; the other should be defined to 0.

## Skipping autodetection¶

CORK_CONFIG_SKIP_AUTODETECT

If you want to skip libcork’s autodetection logic, then you are responsible for providing the appropriate values for all of the macros defined in Configuration macros. To do this, have your build system define this macro, with a value of 1. This will override the default value of 0 provided in the libcork/config/config.h header file.

Then, create (or have your build system create) a libcork/config/custom.h header file. You can place this file anywhere in your header search path. We will load that file instead of libcork’s autodetection logic. Place the appropriate definitions for each of the configuration macros into this file. If needed, you can generate this file as part of the configure step of your build system; the only requirement is that it’s available once you start compiling the libcork source files.