[SCM] GNU Autoconf source repository branch, master, updated. v2.68-29-ge3b2543

[Ralf Wildenhues]

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- Log -----------------------------------------------------------------
commit e3b2543cbf5af1c0f5511a774438fecfb7705efd
Author: Ralf Wildenhues <address@hidden>
Date:   Sun Jan 23 11:24:02 2011 +0100

    docs: new section about whitespace trimmmed from make command-lines.
    
    * doc/autoconf.texi (Command-line Macros and whitespace): New
    section, document trimming of whitespace from macros set on the
    command line and from the environment.
    
    Signed-off-by: Ralf Wildenhues <address@hidden>

commit 80ca89f803a12d1ad674ca8c3f27a7966e2cf968
Author: Ralf Wildenhues <address@hidden>
Date:   Sat Jan 22 19:39:29 2011 +0100

    docs: document how to use comment characters in rules.
    
    * doc/autoconf.texi (Comments in Make Rules): Explain how to
    produce a `#' in a rule.
    (Comments in Make Macros): Add cross reference.
    Suggestion from Eric Blake.
    
    Signed-off-by: Ralf Wildenhues <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog         |   13 +++++++++++++
 doc/autoconf.texi |   40 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 67d30fc..2fc5ab3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,18 @@
+2011-01-23  Ralf Wildenhues  <address@hidden>
+
+       docs: new section about whitespace trimmmed from make command-lines.
+       * doc/autoconf.texi (Command-line Macros and whitespace): New
+       section, document trimming of whitespace from macros set on the
+       command line and from the environment.
+
 2011-01-22  Ralf Wildenhues  <address@hidden>
 
+       docs: document how to use comment characters in rules.
+       * doc/autoconf.texi (Comments in Make Rules): Explain how to
+       produce a `#' in a rule.
+       (Comments in Make Macros): Add cross reference.
+       Suggestion from Eric Blake.
+
        docs: new sections about comments and whitespace in make macros.
        * doc/autoconf.texi (Top, Portable Make): Adjust menus.
        (Comments in Make Macros, Trailing whitespace in Make Macros):
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 110f5f5..ae601a0 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -535,6 +535,7 @@ Portable Make Programming
 * Newlines in Make Rules::      Using literal newlines in rules
 * Comments in Make Macros::     Other problems with Make comments in macros
 * Trailing whitespace in Make Macros::  Macro substitution problems
+* Command-line Macros and whitespace::  Whitespace trimming of values
 * obj/ and Make::               Don't name a subdirectory @file{obj}
 * make -k Status::              Exit status of @samp{make -k}
 * VPATH and Make::              @code{VPATH} woes
@@ -19141,6 +19142,7 @@ itself.
 * Newlines in Make Rules::      Using literal newlines in rules
 * Comments in Make Macros::     Other problems with Make comments in macros
 * Trailing whitespace in Make Macros::  Macro substitution problems
+* Command-line Macros and whitespace::  Whitespace trimming of values
 * obj/ and Make::               Don't name a subdirectory @file{obj}
 * make -k Status::              Exit status of @samp{make -k}
 * VPATH and Make::              @code{VPATH} woes
@@ -19553,6 +19555,21 @@ all:
         : "foo"
 @end example
 
+Conversely, if you want to use the @samp{#} character in some command,
+you can only do so by expanding it inside a rule (@pxref{Comments in
+Make Macros}).  So for example, if @samp{COMMENT_CHAR} is substituted by
address@hidden as @samp{#}, then the following substitutes
address@hidden@@COMMENT_CHAR@@} in a generated header:
+
address@hidden
+foo.h: foo.h.in
+        sed -e 's|@@''COMMENT_CHAR''@@|@@COMMENT_CHAR@@|g' \
+            $(srcdir)/foo.h.in > $@@
address@hidden example
+
+The funny shell quoting avoids a substitution at @command{config.status}
+run time of the left-hand side of the @command{sed} @samp{s} command.
+
 @node Newlines in Make Rules
 @section Newlines in Make Rules
 @cindex Newlines in @file{Makefile} rules
@@ -19599,7 +19616,8 @@ CPPFLAGS = "-DCOMMENT_CHAR='#'"
 @noindent
 as @samp{CPPFLAGS} may be expanded to @samp{"-DCOMMENT_CHAR='}.
 Luckily, most @command{make} implementations disregard this and treat
-single and double quotes specially here.
+single and double quotes specially here; @pxref{Comments in Make Rules},
+for a more portable alternative.
 
 Even without quoting involved, comments can have surprising effects,
 because the whitespace before them is part of the variable value:
@@ -19630,6 +19648,26 @@ print: ; @@echo $(foo:=.test)
 @noindent
 prints @samp{bar.test .test}.
 
address@hidden Command-line Macros and whitespace
address@hidden Command-line Macros and whitespace
address@hidden whitespace in command-line macros
address@hidden command-line, macros set on
address@hidden environment, macros set from
+
+Some @command{make} implementations may strip trailing whitespace off
+of macros set on the command line in addition to leading whitespace.
+Further, some may strip leading whitespace off of macros set from
+environment variables:
+
address@hidden
+$ @kbd{echo 'print: ; @@echo "x$(foo)x$(bar)x"' |
+  foo=' f f ' make -f - bar=' b b '}
+x f f xb b x  # AIX, BSD, GNU make
+xf f xb b x   # HP-UX, IRIX, Tru64/OSF make
+x f f xb bx   # Solaris make
address@hidden example
+
+
 @node obj/ and Make
 @section The @file{obj/} Subdirectory and Make
 @cindex @file{obj/}, subdirectory


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