FYI: HP cannot cross-compile

[Akim Demaille]

I'd like to have opinion on this documentation, especially the section
name etc.  Better yet: just FIXME :)

Index: ChangeLog
from  Akim Demaille  <address@hidden>

        * tests/semantics.at (AC_CHECK_SIZEOF): Split into two tests: one
        for plain code, the other for cross-compilation code.  The latter
        is now run with GCC only.
        * doc/autoconf.texi (Compilers and Preprocessors): New.

Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.578
diff -u -u -r1.578 autoconf.texi
--- doc/autoconf.texi 30 Jan 2002 13:08:45 -0000 1.578
+++ doc/autoconf.texi 30 Jan 2002 15:10:33 -0000
@@ -274,6 +274,7 @@
 
 Compilers and Preprocessors
 
+* Specific Compiler Characteristics::  Some portability issues
 * Generic Compiler Characteristics::  Language independent tests
 * C Compiler::                  Checking its characteristics
 * C++ Compiler::                Likewise
@@ -4633,11 +4634,46 @@
 compiling.
 
 @menu
+* Specific Compiler Characteristics::  Some portability issues
 * Generic Compiler Characteristics::  Language independent tests
 * C Compiler::                  Checking its characteristics
 * C++ Compiler::                Likewise
 * Fortran 77 Compiler::         Likewise
 @end menu
+
address@hidden Specific Compiler Characteristics
address@hidden Specific Compiler Characteristics
+
+Some compilers exhibit different behaviors.
+
address@hidden @asis
address@hidden Static/Dynamic Expressions
+Autoconf relies on a trick to extract one bit of information from the C
+compiler: using negative array sizes.  For instance the following
+excerpt of a C source demonstrates how to test whether @samp{int}s are 4
+bytes long:
+
address@hidden
+int
+main (void)
address@hidden
+  static int test_array [(unsigned long) (sizeof (int)) == 4 ? 1 : -1];
+  test_array [0] = 0
+  return 0;
address@hidden
address@hidden example
+
address@hidden
+To our knowledge, there is a single compiler that does not support this
+trick: the HP C compilers (the real one, not only the ``bundled'') on
+HP-UX 11.00:
+
address@hidden
+$ @kbd{cc -c -Ae +O2 +Onolimit conftest.c}
+cc: "conftest.c": error 1879: Variable-length arrays cannot \
+    have static storage.
address@hidden example
address@hidden table
 
 @node Generic Compiler Characteristics
 @subsection Generic Compiler Characteristics
Index: tests/semantics.at
===================================================================
RCS file: /cvsroot/autoconf/autoconf/tests/semantics.at,v
retrieving revision 1.34
diff -u -u -r1.34 semantics.at
--- tests/semantics.at 13 Sep 2001 06:53:19 -0000 1.34
+++ tests/semantics.at 30 Jan 2002 15:10:33 -0000
@@ -156,27 +156,48 @@
 
 # AC_CHECK_SIZEOF
 # ---------------
+# Not cross-compiling.
 AT_CHECK_MACRO([AC_CHECK_SIZEOF],
 [[AC_CHECK_SIZEOF(char)
 AC_CHECK_SIZEOF(charchar,,
 [[#include <stdio.h>
 typedef char charchar[2];]])
 AC_CHECK_SIZEOF(charcharchar)
+]],
+[AT_CHECK_DEFINES(
+[#define SIZEOF_CHAR 1
+#define SIZEOF_CHARCHAR 2
+#define SIZEOF_CHARCHARCHAR 0
+])])
+
 
-# Exercize the code used when cross-compiling
+# AC_CHECK_SIZEOF
+# ---------------
+# Cross-compiling: only with GCC, as some compilers, such as HP's
+# cannot grok our trick:
+#
+# static int test_array [1 - 2 * !(((unsigned long) (sizeof (unsigned char))) 
>= 0)];
+#
+# configure:3637: cc -c -Ae +O2 +Onolimit  conftest.c >&5
+# cc: "configure", line 3660: error 1879: Variable-length arrays cannot have 
static storage.
+#
+AT_CHECK_MACRO([AC_CHECK_SIZEOF],
+[[# Exercize the code used when cross-compiling
+AC_PROG_CC
+if test "$GCC" != yes; then
+  exit 77
+fi
 cross_compiling=yes
-AC_CHECK_SIZEOF(unsigned char)
-AC_CHECK_SIZEOF(ucharchar,,
+AC_CHECK_SIZEOF(char)
+AC_CHECK_SIZEOF(charchar,,
 [[#include <stdio.h>
-typedef unsigned char ucharchar[2];]])
-AC_CHECK_SIZEOF(ucharcharchar)]],
+typedef char charchar[2];]])
+AC_CHECK_SIZEOF(charcharchar)
+]],
 [AT_CHECK_DEFINES(
 [#define SIZEOF_CHAR 1
 #define SIZEOF_CHARCHAR 2
 #define SIZEOF_CHARCHARCHAR 0
-#define SIZEOF_UCHARCHAR 2
-#define SIZEOF_UCHARCHARCHAR 0
-#define SIZEOF_UNSIGNED_CHAR 1
 ])])