[PATCH 4/4] Work around DJGPP shell function return bug with command substitutions.

[Ralf Wildenhues]

DJGPP bash 2.04 has a bug in that `return $ac_retval' done in a
shell function which also contains a command substitution causes
the shell to barf.  For more details see
<http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp/2006/08/08/16:37:27>.
Possible workaround include putting the `return' in a subshell
or calling another function to set the status.

* lib/autoconf/general.m4 (_AC_PREPROC_IFELSE_BODY)
(_AC_COMPILE_IFELSE_BODY, _AC_LINK_IFELSE_BODY)
(_AC_RUN_IFELSE_BODY, _AC_COMPUTE_INT_BODY): Use AS_SET_STATUS
instead of `return'.
* doc/autoconf.texi (Common Shell Constructs, Shell Functions):
Document the issue.
* THANKS: Update.
Report by Rugxulo and Reuben Thomas.
---

* Ralf Wildenhues wrote on Sun, Sep 13, 2009 at 09:12:28PM CEST:
> -- Failures due to some obscure DJGPP shell bug with 'return $ac_retval'
> worked around with patch.
> 
> Test failures: not recorded (several instances though)

While there is a fix for upstream for this bug now, it is prudent to
still work around it, so users that haven't updated can work too.

Can we have a full name to put in THANKS (change omitted here)?

Thanks,
Ralf

 THANKS                  |    1 +
 doc/autoconf.texi       |   10 +++++++++-
 lib/autoconf/general.m4 |   10 +++++-----
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 32e6683..b1dbac3 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -12692,7 +12692,9 @@ Common Shell Constructs
 Emit shell code to set the value of @samp{$?} to @var{status}, as
 efficiently as possible.  However, this is not guaranteed to abort a
 shell running with @code{set -e} (@pxref{set, , Limitations of Shell
-Builtins}).
+Builtins}).  This should also be used at the end of a complex shell
+function instead of @samp{return} (@pxref{Shell Functions}) to avoid
+a DJGPP shell bug.
 @end defmac
 
 @defmac AS_TR_CPP (@var{expression})
@@ -15503,6 +15505,12 @@ Shell Functions
 2
 @end example
 
+DJGPP bash 2.04 has a bug in that @command{return} from a shell function
+which also used a command substitution causes a segmentation fault.
+Details are not unclear; to work around the issue, you can use
address@hidden from a subshell, or @samp{AS_SET_STATUS} as last command
+in the execution flow of the function (@pxref{Common Shell Constructs}).
+
 Not all shells treat shell functions as simple commands impacted by
 @samp{set -e}, for example with Solaris 10 @command{bin/sh}:
 
diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index fd40c43..a4271bc 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -2457,7 +2457,7 @@ m4_define([_AC_PREPROC_IFELSE_BODY],
     [_AC_MSG_LOG_CONFTEST
     ac_retval=1])
   AS_LINENO_POP
-  return $ac_retval
+  AS_SET_STATUS([$ac_retval])
 ])# _AC_PREPROC_IFELSE_BODY
 
 
@@ -2546,7 +2546,7 @@ m4_define([_AC_COMPILE_IFELSE_BODY],
       [_AC_MSG_LOG_CONFTEST
        ac_retval=1])
   AS_LINENO_POP
-  return $ac_retval
+  AS_SET_STATUS([$ac_retval])
 ])# _AC_COMPILE_IFELSE_BODY
 
 
@@ -2610,7 +2610,7 @@ m4_define([_AC_LINK_IFELSE_BODY],
   # left behind by Apple's compiler.  We do this before executing the actions.
   rm -rf conftest.dSYM conftest_ipa8_conftest.oo
   AS_LINENO_POP
-  return $ac_retval
+  AS_SET_STATUS([$ac_retval])
 ])# _AC_LINK_IFELSE_BODY
 
 
@@ -2682,7 +2682,7 @@ m4_define([_AC_RUN_IFELSE_BODY],
        ac_retval=$ac_status])
   rm -rf conftest.dSYM conftest_ipa8_conftest.oo
   AS_LINENO_POP
-  return $ac_retval
+  AS_SET_STATUS([$ac_retval])
 ])# _AC_RUN_IFELSE_BODY
 
 
@@ -3004,7 +3004,7 @@ m4_define([_AC_COMPUTE_INT_BODY],
                        [ac_retval=0], [ac_retval=1])
   fi
   AS_LINENO_POP
-  return $ac_retval
+  AS_SET_STATUS([$ac_retval])
 ])# _AC_COMPUTE_INT_BODY
 
 # AC_COMPUTE_INT(VARIABLE, EXPRESSION, PROLOGUE, [IF-FAILS])
-- 
1.6.3.3.345.gb7132