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Create the header-file and let it contain ’#defines’ for the target platform. This macro is used for libraries that have platform-specific quirks. Instead of inventing a target-specific files, just let it create a header file from the definitions of AC_CANONICAL_SYSTEM and put only ifdef’s in the installed header-files.

 if the HEADER-FILE is absent, [target.h] is used.
 if the PREFIX is absent, [TARGET] is used.
 the prefix can be the packagename. (y:a-z-:A-Z_:)

The defines look like...

 #ifndef TARGET_CPU_M68K
 #define TARGET_CPU_M68K "m68k"
 #define TARGET_OS_LINUX "linux-gnu"
 #ifndef TARGET_OS_TYPE                     /* the string itself */
 #define TARGET_OS_TYPE "linux-gnu"

Detail: in the case of hppa1.1, the three idents "hppa1_1" "hppa1" and "hppa" are derived, for an m68k it just two, "m68k" and "m".

The CREATE_TARGET_H__ variant is almost the same function, but everything is lowercased instead of uppercased, and there is a "__" in front of each prefix, so it looks like...

 #ifndef __target_os_linux
 #define __target_os_linux "linux-gnulibc2"
 #ifndef __target_os__                     /* the string itself */
 #define __target_os__ "linux-gnulibc2"
 #ifndef __target_cpu_i586
 #define __target_cpu_i586 "i586"
 #ifndef __target_arch_i386
 #define __target_arch_i386 "i386"
 #ifndef __target_arch__                   /* cpu family arch */
 #define __target_arch__ "i386"

Other differences: the default string-define is "__" instead of "_TYPE".

Personally, I prefer the second variant (which had been the first in the devprocess of this file but I assume people will often fallback to the primary variant presented herein).

NOTE: CREATE_TARGET_H does also fill HOST_OS-defines Functionality has been split over functions called CREATE_TARGET_H_UPPER, CREATE_TARGET_H_LOWER, CREATE_TARGET_HOST_UPPER, and CREATE_TARGET_HOST_LOWER.


There is now a CREATE_PREFIX_TARGET_H in this file as a shorthand for PREFIX_CONFIG_H from a target.h file, however w/o the target.h ever created (the prefix is a bit different, since we add an extra -target- and -host-).

Source Code

Download the latest version of ax_create_target_h.m4 or browse the macro’s revision history.


Copyright © 2008 Guido U. Draheim

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

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