AX_PROTOTYPE(function, includes, code, TAG1, values1 [, TAG2, values2 [...]])
Try all the combinations of <TAG1>, <TAG2>... to successfully compile <code>. <TAG1>, <TAG2>, ... are substituted in <code> and <include> with values found in <values1>, <values2>, ... respectively. <values1>, <values2>, ... contain a list of possible values for each corresponding tag and all combinations are tested. When AC_TRY_COMPILE(include, code) is successful for a given substitution, the macro stops and defines the following macros: FUNCTION_TAG1, FUNCTION_TAG2, ... using AC_DEFINE() with values set to the current values of <TAG1>, <TAG2>, ... If no combination is successful the configure script is aborted with a message.
Intended purpose is to find which combination of argument types is acceptable for a given function <function>. It is recommended to list the most specific types first. For instance ARG1, [size_t, int] instead of ARG1, [int, size_t].
Generic usage pattern:
1) add a call in configure.in
2) call autoheader to see which symbols are not covered
3) add the lines in acconfig.h
/* Type of Nth argument of function */ #undef FUNCTION_ARGN
4) Within the code use FUNCTION_ARGN instead of an hardwired type
AX_PROTOTYPE(getpeername, [ #include <sys/types.h> #include <sys/socket.h> ], [ int a = 0; ARG2 * b = 0; ARG3 * c = 0; getpeername(a, b, c); ], ARG2, [struct sockaddr, void], ARG3, [socklen_t, size_t, int, unsigned int, long unsigned int])
2) call autoheader
autoheader: Symbol `GETPEERNAME_ARG2' is not covered by ./acconfig.h autoheader: Symbol `GETPEERNAME_ARG3' is not covered by ./acconfig.h
/* Type of second argument of getpeername */ #undef GETPEERNAME_ARG2
/* Type of third argument of getpeername */ #undef GETPEERNAME_ARG3
4) in the code
... GETPEERNAME_ARG2 name; GETPEERNAME_ARG3 namelen; ... ret = getpeername(socket, &name, &namelen); ...
Implementation notes: generating all possible permutations of the arguments is not easily done with the usual mixture of shell and m4, that is why this macro is almost 100% m4 code. It generates long but simple to read code.
Download the latest version of ax_prototype.m4 or browse the macro’s revision history.
Copyright © 2009 Loic Dachary email@example.com
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