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Formerly make.texinfo.~119~

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Roland McGrath 1993-09-17 07:33:03 +00:00
parent b018db955c
commit 5174a5e5a1
1 changed files with 14 additions and 8 deletions
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@ -9,7 +9,7 @@
@set EDITION 0.44
@set VERSION 3.69 Beta
@set UPDATED 6 September 1993
@set UPDATED 17 September 1993
@set UPDATE-MONTH September 1993
@c finalout
@ -1558,10 +1558,11 @@ expansion happens in the rule for @file{foo}, so that each @emph{existing}
@samp{.o} file becomes a dependency of @file{foo} and will be recompiled if
necessary.
But what if you delete all the @samp{.o} files? Then @samp{*.o} will
expand into @emph{nothing}. The target @file{foo} will have no
dependencies and would be remade by linking no object files. This is not
what you want!
But what if you delete all the @samp{.o} files? When a wildcard matches
no files, it is left as it is, so then @file{foo} will depend on the
oddly-named file @file{*.o}. Since so such file is likely to exist,
@code{make} will give you an error saying it cannot figure out how to
make @file{*.o}. This is not what you want!
Actually it is possible to obtain the desired result with wildcard
expansion, but you need more sophisticated techniques, including the
@ -1583,12 +1584,17 @@ arguments of a function. If you want to do wildcard expansion in such
places, you need to use the @code{wildcard} function, like this:
@example
$(wildcard @var{pattern})
$(wildcard @var{pattern}@dots{})
@end example
@noindent
This string, used anywhere in a makefile, is replaced by a space-separated
list of names of existing files that match the pattern @var{pattern}.
This string, used anywhere in a makefile, is replaced by a
space-separated list of names of existing files that match one of the
given file name patterns. If no existing file name matches a pattern,
then that pattern is omitted from the output of the @code{wildcard}
function. Note that this is different from how unmatched wildcards
behave in rules, where they are used verbatim rather than ignored
(@pxref{Wildcard Pitfall}).
One use of the @code{wildcard} function is to get a list of all the C source
files in a directory, like this: