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Replace documentation for obsolete AC_LIBOBJ_DECL with clearer

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documentation for AC_LIBSOURCE and AC_LIBSOURCES, improving the
AC_LIBOBJ docs as well.
This commit is contained in:
Steven G. Johnson 2001-04-18 04:26:08 +00:00
parent 273bd6c545
commit fb3e27e1a2
1 changed files with 42 additions and 25 deletions
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doc/autoconf.texi
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@ -3397,8 +3397,9 @@ specific files, and then program as if you were in a @sc{posix}
environment. Some functions may be missing or unfixable, and your
package must be ready to replace them.
Use the first two following macros to specify a function to be replaced,
and use the third one to check for and replace the function if needed.
Use the first three of the following macros to specify a function to be
replaced, and the last one (@code{AC_REPLACE_FUNCS}) to check for and
replace the function if needed.
@defmac AC_LIBOBJ (@var{function})
@maindex LIBOBJ
@ -3406,45 +3407,61 @@ and use the third one to check for and replace the function if needed.
Specify that @samp{@var{function}.c} must be included in the executables
to replace a missing or broken implementation of @var{function}.
Technically it adds @samp{@var{function}.$ac_objext} to the output
variable @code{LIBOBJS}, nevertheless you must not directly change
@code{LIBOBJS} since this is not traceable.
Technically, it adds @samp{@var{function}.$ac_objext} to the output
variable @code{LIBOBJS} and calls @code{AC_LIBSOURCE} for
@samp{@var{function}.c}. You should not directly change @code{LIBOBJS},
since this is not traceable.
@end defmac
@defmac AC_LIBOBJ_DECL (@var{function})
@maindex LIBOBJ_DECL
@ovindex LIBOBJS
Specify that @samp{@var{function}.c} might be needed to compile the
project. You must use this macro when you are calling @code{AC_LIBOBJ}
with a shell variable, since shell variables cannot be traced
statically. @var{function} must be a literal.
@defmac AC_LIBSOURCE (@var{file})
@maindex LIBSOURCE
Specify that @var{file} might be needed to compile the project. If you
need to know what files might be needed by a @file{configure.ac}, you
should trace @code{AC_LIBSOURCE}. @var{file} must be a literal.
For instance you might need to:
This macro is called automatically from @code{AC_LIBOBJ}, but you must
call it explicitly if you pass a shell variable to @code{AC_LIBOBJ}. In
that case, since shell variables cannot be traced statically, you must
pass to @code{AC_LIBSOURCE} any possible files that the shell variable
might cause @code{AC_LIBOBJ} to need. For example, if you want to pass
a variable @code{$foo_or_bar} to @code{AC_LIBOBJ} that holds either
@code{"foo"} or @code{"bar"}, you should do:
@example
AC_LIBOBJ_DECL(foo)
AC_LIBOBJ_DECL(bar)
AC_LIBSOURCE(foo.c)
AC_LIBSOURCE(bar.c)
AC_LIBOBJ($foo_or_bar)
@end example
@noindent
nevertheless, there is always a means to avoid this, and you are
encouraged to always uses literals with @code{AC_LIBOBJ}.
There is usually a way to avoid this, however, and you are encouraged to
simply call @code{AC_LIBOBJ} with literal arguments.
Conversely, if you need to know what are the files that might be needed
by a @file{configure.ac}, you should trace @code{AC_LIBOBJ_DECL}.
Note that this macro replaces the obsolete @code{AC_LIBOBJ_DECL}, with
slightly different semantics: the old macro took the function name,
e.g. @code{foo}, as its argument rather than the file name.
@end defmac
@defmac AC_LIBSOURCES (@var{files})
@maindex LIBSOURCES
Like @code{AC_LIBSOURCE}, but accepts one or more @var{files} in a
comma-separated M4 list. Thus, the above example might be rewritten:
@example
AC_LIBSOURCES([foo.c, bar.c])
AC_LIBOBJ($foo_or_bar)
@end example
@end defmac
@defmac AC_REPLACE_FUNCS (@var{function}@dots{})
@maindex REPLACE_FUNCS
@ovindex LIBOBJS
Like calling @code{AC_CHECK_FUNCS}, but using
@samp{AC_LIBOBJ(@var{function})} as @var{action-if-not-found}. You can
declare your replacement function by enclosing the prototype in
@samp{#if !HAVE_@var{function}}. If the system has the function, it
probably declares it in a header file you should be including, so you
shouldn't redeclare it lest your declaration conflict.
Like @code{AC_CHECK_FUNCS}, but uses @samp{AC_LIBOBJ(@var{function})} as
@var{action-if-not-found}. You can declare your replacement function by
enclosing the prototype in @samp{#if !HAVE_@var{function}}. If the
system has the function, it probably declares it in a header file you
should be including, so you shouldn't redeclare it lest your declaration
conflict.
@end defmac
@node Header Files, Declarations, Library Functions, Existing Tests