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Diffstat (limited to 'doc/autoconf.texi')
| -rw-r--r-- | doc/autoconf.texi | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/doc/autoconf.texi b/doc/autoconf.texi index 90ab4b9e..3d990125 100644 --- a/doc/autoconf.texi +++ b/doc/autoconf.texi @@ -20256,14 +20256,37 @@ However, this rule leads to real problems in practice. For example, if the source directory contains an ordinary file named @file{test} that is used in a dependency, Solaris @command{make} rewrites commands like @samp{if test -r foo; @dots{}} to @samp{if ../pkg/src/test -r foo; -@dots{}}, which is typically undesirable. To avoid this problem, -portable makefiles should never mention a source file whose name is that -of a shell keyword like @file{until} or a shell command like -@command{cat} or @command{gcc} or @command{test}. - -Because of these problems GNU @command{make} and many other -@command{make} implementations do not rewrite commands, so portable -makefiles should +@dots{}}, which is typically undesirable. In fact, @command{make} is +completely unaware of shell syntax used in the rules, so the VPATH +rewrite can potentially apply to @emph{any} whitespace-separated word +in a rule, including shell variables, functions, and keywords. + +@example +$ @kbd{mkdir build} +$ @kbd{cd build} +$ @kbd{cat > Makefile <<'END'} +VPATH = .. +all: arg func for echo + func () @{ for arg in "$$@@"; do echo $$arg; done; @}; \ + func "hello world" +END +$ @kbd{touch ../arg ../func ../for ../echo} +$ @kbd{make} +../func () @{ ../for ../arg in "$@@"; do ../echo $arg; done; @}; \ +../func "hello world" +sh: syntax error at line 1: `do' unexpected +*** Error code 2 +@end example + +@noindent +To avoid this problem, portable makefiles should never mention a source +file or dependency whose name is that of a shell keyword like @file{for} +or @file{until}, a shell command like @command{cat} or @command{gcc} or +@command{test}, or a shell function or variable used in the corresponding +@command{Makefile} recipe. + +Because of these problems GNU @command{make} and many other @command{make} +implementations do not rewrite commands, so portable makefiles should search @code{VPATH} manually. It is tempting to write this: @smallexample |