Re: branch-1_4 - platform recognition macro

[Eric Blake]

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According to Eric Blake on 6/30/2006 12:39 PM:
> 2006-06-30  Eric Blake  <address@hidden>
> 
>       For compatibility with other m4 implementations, sysval returns
>       signal<<8 rather than 0 if syscmd is terminated by a signal.
>       * configure.ac (AC_CHECK_HEADERS_ONCE): Check for sys/wait.h.
>       * src/builtin.c (include): Include sys/wait.h when stdlib.h does
>       not provide wait macros.

Ported this portion of the patch to head as follows.  Note that the OS/2
portion, where we added .m4 code to configure to check for a broken
system() call, has not been ported yet (but I'm not even sure how libtool
fares on OS/2, to be worried about that port just yet).  I still have
quite a bit of porting to do in m4.texinfo, including the tests that the
branch had that exercise this code.

2006-08-21  Eric Blake  <address@hidden>

        * configure.ac (AC_CHECK_HEADERS_ONCE): Check for <sys/wait.h>.
        * modules/gnu.c (esyscmd): Use -1 for failure.  Set sysval to 0
        when no arguments are given, but without losing warning about 0
        arguments.
        * modules/m4.c (syscmd): Likewise.
        (includes): Assume C89.
        (m4_sysval): Make static.
        (M4_SYSVAL_EXITBITS, M4_SYSVAL_TERMSIGBITS): New macros.
        (sysval): Port calculation from branch.

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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Index: configure.ac
===================================================================
RCS file: /sources/m4/m4/configure.ac,v
retrieving revision 1.52
diff -u -p -r1.52 configure.ac
--- configure.ac        9 Aug 2006 13:16:34 -0000       1.52
+++ configure.ac        21 Aug 2006 12:38:48 -0000
@@ -168,7 +168,7 @@ AC_CHECK_SIZEOF([long long int])
 ## ------------------------- ##
 ## C headers required by M4. ##
 ## ------------------------- ##
-AC_CHECK_HEADERS_ONCE([limits.h])
+AC_CHECK_HEADERS_ONCE([limits.h sys/wait.h])
 
 if test $ac_cv_header_stdbool_h = yes; then
   INCLUDE_STDBOOL_H='#include <stdbool.h>'
Index: modules/gnu.c
===================================================================
RCS file: /sources/m4/m4/modules/gnu.c,v
retrieving revision 1.48
diff -u -p -r1.48 gnu.c
--- modules/gnu.c       21 Aug 2006 02:37:45 -0000      1.48
+++ modules/gnu.c       21 Aug 2006 12:38:48 -0000
@@ -53,7 +53,7 @@
        BUILTIN(changesyntax,   false,  true,   1,      -1 )    \
        BUILTIN(debugmode,      false,  false,  1,      2  )    \
        BUILTIN(debugfile,      false,  false,  1,      2  )    \
-       BUILTIN(esyscmd,        false,  true,   2,      2  )    \
+       BUILTIN(esyscmd,        false,  true,   -1,     2  )    \
        BUILTIN(format,         false,  true,   2,      -1 )    \
        BUILTIN(indir,          false,  true,   2,      -1 )    \
        BUILTIN(patsubst,       false,  true,   3,      5  )    \
@@ -126,7 +126,7 @@ m4_regexp_compile (m4 *context, const ch
      use a static variable.  To be reentrant, we would need a mutex in
      this method, and we should have a way to free the memory used by
      buf when this module is unloaded.  */
-  
+
   static m4_pattern_buffer buf;        /* compiled regular expression */
   const char *msg;             /* error message from re_compile_pattern */
 
@@ -468,6 +468,16 @@ M4BUILTIN_HANDLER (esyscmd)
       FILE *pin;
       int ch;
 
+      /* Calling with no arguments triggers a warning, but must also
+         set sysval to 0 as if the empty command had been executed.
+         Therefore, we must manually check min args ourselves rather
+         than relying on the macro calling engine.  */
+      if (m4_bad_argc (context, argc, argv, 2, -1))
+        {
+          m4_set_sysval (0);
+          return;
+        }
+
       m4_sysval_flush (context);
       errno = 0;
       pin = popen (M4ARG (1), "r");
@@ -476,7 +486,7 @@ M4BUILTIN_HANDLER (esyscmd)
          m4_error (context, 0, errno,
                    _("%s: cannot open pipe to command `%s'"),
                    M4ARG (0), M4ARG (1));
-         m4_set_sysval (0xffff);
+         m4_set_sysval (-1);
        }
       else
        {
Index: modules/m4.c
===================================================================
RCS file: /sources/m4/m4/modules/m4.c,v
retrieving revision 1.64
diff -u -p -r1.64 m4.c
--- modules/m4.c        9 Aug 2006 21:33:24 -0000       1.64
+++ modules/m4.c        21 Aug 2006 12:38:48 -0000
@@ -21,20 +21,14 @@
 #  include <config.h>
 #endif
 
-#if HAVE_STDLIB_H
-#  include <stdlib.h>
-#endif
-
-#if HAVE_UNISTD_H
-#  include <unistd.h>
-#endif
-
+#include <assert.h>
 #include <errno.h>
-#ifndef errno
-extern int errno;
-#endif
+#include <stdlib.h>
+#include <unistd.h>
 
-#include <assert.h>
+#if HAVE_SYS_WAIT_H
+# include <sys/wait.h>
+#endif
 
 #include <m4module.h>
 #include <modules/m4.h>
@@ -92,7 +86,7 @@ extern const char *m4_expand_ranges (con
        BUILTIN(shift,          false,  false,  0,      -1 )    \
        BUILTIN(sinclude,       false,  true,   2,      2  )    \
        BUILTIN(substr,         false,  true,   3,      4  )    \
-       BUILTIN(syscmd,         false,  true,   2,      2  )    \
+       BUILTIN(syscmd,         false,  true,   -1,     2  )    \
        BUILTIN(sysval,         false,  false,  0,      -1 )    \
        BUILTIN(traceoff,       false,  false,  0,      -1 )    \
        BUILTIN(traceon,        false,  false,  0,      -1 )    \
@@ -427,11 +421,40 @@ Warning: %s: builtin `%s' requested by f
    and "sysval".  */
 
 /* Exit code from last "syscmd" command.  */
-int  m4_sysval = 0;
+/* FIXME - we should preserve this value across freezing.  See
+   http://lists.gnu.org/archive/html/bug-m4/2006-06/msg00059.html
+   for ideas on how do to that.  */
+static int  m4_sysval = 0;
+
+/* Helper macros for readability.  */
+#if UNIX || defined WEXITSTATUS
+# define M4_SYSVAL_EXITBITS(status)                       \
+   (WIFEXITED (status) ? WEXITSTATUS (status) : 0)
+# define M4_SYSVAL_TERMSIGBITS(status)                    \
+   (WIFSIGNALED (status) ? WTERMSIG (status) << 8 : 0)
+
+#else /* ! UNIX && ! defined WEXITSTATUS */
+/* Platforms such as mingw do not support the notion of reporting
+   which signal terminated a process.  Furthermore if WEXITSTATUS was
+   not provided, then the exit value is in the low eight bits.  */
+# define M4_SYSVAL_EXITBITS(status) status
+# define M4_SYSVAL_TERMSIGBITS(status) 0
+#endif /* ! UNIX && ! defined WEXITSTATUS */
 
+/* Fallback definitions if <stdlib.h> or <sys/wait.h> are inadequate.  */
+/* FIXME - this may fit better as a gnulib module.  */
 #ifndef WEXITSTATUS
 # define WEXITSTATUS(status) (((status) >> 8) & 0xff)
 #endif
+#ifndef WTERMSIG
+# define WTERMSIG(status) ((status) & 0x7f)
+#endif
+#ifndef WIFSIGNALED
+# define WIFSIGNALED(status) (WTERMSIG (status) != 0)
+#endif
+#ifndef WIFEXITED
+# define WIFEXITED(status) (WTERMSIG (status) == 0)
+#endif
 
 void
 m4_set_sysval (int value)
@@ -451,14 +474,28 @@ m4_sysval_flush (m4 *context)
 
 M4BUILTIN_HANDLER (syscmd)
 {
+  /* Calling with no arguments triggers a warning, but must also set
+     sysval to 0 as if the empty command had been executed.
+     Therefore, we must manually check min args ourselves rather than
+     relying on the macro calling engine.  */
+  if (m4_bad_argc (context, argc, argv, 2, -1))
+    {
+      m4_set_sysval (0);
+      return;
+    }
   m4_sysval_flush (context);
   m4_sysval = system (M4ARG (1));
+  /* FIXME - determine if libtool works for OS/2, in which case the
+     FUNC_SYSTEM_BROKEN section on the branch must be ported to work
+     around the bug in their EMX libc system().  */
 }
 
 
 M4BUILTIN_HANDLER (sysval)
 {
-  m4_shipout_int (obs, WEXITSTATUS (m4_sysval));
+  m4_shipout_int (obs, (m4_sysval == -1 ? 127
+                        : (M4_SYSVAL_EXITBITS (m4_sysval)
+                           | M4_SYSVAL_TERMSIGBITS (m4_sysval))));
 }