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Document Solaris ‘make’ glitch with ‘!’

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* doc/autoconf.texi (Failure in Make Rules):
Document that there are some complicated exceptions to
the idea that sh -e exits if any subcommand fails.
(Command Line Prefixes): New section.
This commit is contained in:
Paul Eggert 2024-06-01 09:07:38 -07:00
parent 056518b94e
commit e51e789ac9
1 changed files with 26 additions and 3 deletions
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@ -527,7 +527,8 @@ Portable Make Programming
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Command Line Prefixes:: What's at the start of makefile command lines
* Special Chars in Names:: Special characters in macro names
* Backslash-Newline-Empty:: Empty lines after backslash-newline
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
@ -20379,7 +20380,8 @@ itself.
@menu
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Command Line Prefixes:: What's at the start of makefile command lines
* Special Chars in Names:: Special characters in macro names
* Backslash-Newline-Empty:: Empty lines after backslash-newline
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
@ -20411,10 +20413,13 @@ later) @command{make} diagnoses these uses and errors out.
@node Failure in Make Rules
@section Failure in Make Rules
Unless errors are being ignored
(e.g., because a makefile command line is preceded by a @samp{-} prefix),
Posix 2008 requires that @command{make} must invoke each command with
the equivalent of a @samp{sh -e -c} subshell, which causes the
subshell to exit immediately if a subsidiary simple-command fails,
although not all @command{make} implementations have historically
with some complicated exceptions.
Historically not all @command{make} implementations
followed this rule. For
example, the command @samp{touch T; rm -f U} may attempt to
remove @file{U} even if the @command{touch} fails, although this is not
@ -20428,6 +20433,24 @@ are worried
about porting to buggy BSD shells it may be simpler to migrate
complicated @command{make} actions into separate scripts.
@node Command Line Prefixes
@section Makefile Command Line Prefixes
Makefile command lines can be preceded by zero or more of
the command line prefixes @samp{-}, @samp{@@}, and @samp{+},
which modify how @command{make} processes the command.
Although Posix says these are the only command line prefixes,
some @command{make} implementations, such as Solaris @command{make},
support the additional prefixes @samp{!} and @samp{?}.
Portable makefiles should therefore avoid using these two characters at
the start of a makefile command line.
For example:
@example
mishandled-by-Solaris-make:; ! grep FIXME foo.c
portable-to-Solaris-make:; :;! grep FIXME foo.c
@end example
@node Special Chars in Names
@section Special Characters in Make Macro Names