Re: `#error' vs string literal

[Paul Eggert]

Ralf Wildenhues <address@hidden> writes:

> Ping.  It'd be nice to know if this has a chance of being acceptable,
> or if I should just drop it.

I installed this instead, as I think it's a bit clearer.

2006-04-06  Paul Eggert  <address@hidden>

        * doc/autoconf.texi (C Compiler): Warn about #error.  Follows up
        on a patch proposed by Ralf Wildenhues.

--- doc/autoconf.texi   5 Apr 2006 22:41:36 -0000       1.984
+++ doc/autoconf.texi   6 Apr 2006 07:58:20 -0000       1.985
@@ -5795,6 +5795,15 @@ This can cause problems if you observe t
 detect failures.  Invoking @samp{cc -c a.c && cc -c b.c && cc -o c a.o
 b.o} solves the issue.
 
address@hidden Don't rely on @code{#error} failing
+The @sc{irix} C compiler does not fail when #error is preprocessed; it
+simply emits a diagnostic and continues, exiting successfully.  So,
+instead of an error directive like @code{#error "Unsupported word size"}
+it is more portable to use an invalid directive like @code{#Unsupported
+word size} in Autoconf tests.  In ordinary source code, @code{#error} is
+OK, since installers with inadequate compilers like @sc{irix} can simply
+examine these compilers' diagnostic output.
+
 @item Don't rely on correct @code{#line} support
 On Solaris 8, @command{c89} (Sun WorkShop 6 update 2 C 5.3 Patch
 111679-08 2002/05/09)) diagnoses @code{#line} directives whose line