[Patch, Fortran] PR 48961 - Fix EXECUTE_COMMAND_LINE w/ wait=.false. for non-fork systems

[Tobias Burnus]

The attached patch fixes three issues:

a) If fork() is not supported, CMDSTAT is -2 (as required by the 
standard) - and everything is executed synchronously. However, 
set_cmdstat will abort if the cmdstat value is not 0.

b) The cmdstat value should be set to an error if  system returns an 
error ("-1") -- also for WAIT=.false.

c) In the synchronous case with WAIT=.false. the EXITSTAT= value was not 
set.

Additionally, I converted some literals to the EXEC_* enum values.

Build on x86-64-linux.
OK for the trunk?

Tobias

PS: The next step would be to add support for asynchronous execution 
under Windows, cf. PR.
2011-05-12  Tobias Burnus  <bur...@net-b.de>

	PR fortran/48961
	* intrinsics/execute_command_line.c (set_cmdstat): Don't abort if
	synchronously executing with WAIT=.false.
	(execute_command_line): Fix setting of cmdstat and exitstat.

diff --git a/libgfortran/intrinsics/execute_command_line.c b/libgfortran/intrinsics/execute_command_line.c
index 4e3c445..d0b79a4 100644
--- a/libgfortran/intrinsics/execute_command_line.c
+++ b/libgfortran/intrinsics/execute_command_line.c
@@ -38,9 +38,12 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #endif
 
 
-enum { EXEC_NOERROR = 0, EXEC_SYSTEMFAILED };
+enum { EXEC_SYNCHRONOUS = -2, EXEC_NOERROR = 0, EXEC_SYSTEMFAILED,
+       EXEC_CHILDFAILED };
 static const char *cmdmsg_values[] =
-  { "", "Execution of child process impossible" };
+  { "",
+    "Termination status of the command-language interpreter cannot be obtained",
+    "Execution of child process impossible" };
 
 
 
@@ -49,7 +52,7 @@ set_cmdstat (int *cmdstat, int value)
 {
   if (cmdstat)
     *cmdstat = value;
-  else if (value != 0)
+  else if (value > EXEC_NOERROR)
     runtime_error ("Could not execute command line");
 }
 
@@ -74,10 +77,10 @@ execute_command_line (const char *command, bool wait, int *exitstat,
       /* Asynchronous execution.  */
       pid_t pid;
 
-      set_cmdstat (cmdstat, 0);
+      set_cmdstat (cmdstat, EXEC_NOERROR);
 
       if ((pid = fork()) < 0)
-	set_cmdstat (cmdstat, EXEC_SYSTEMFAILED);
+	set_cmdstat (cmdstat, EXEC_CHILDFAILED);
       else if (pid == 0)
 	{
 	  /* Child process.  */
@@ -91,13 +94,15 @@ execute_command_line (const char *command, bool wait, int *exitstat,
       /* Synchronous execution.  */
       int res = system (cmd);
 
-      if (!wait)
-	set_cmdstat (cmdstat, -2);
-      else if (res == -1)
+      if (res == -1)
 	set_cmdstat (cmdstat, EXEC_SYSTEMFAILED);
+      else if (!wait)
+	set_cmdstat (cmdstat, EXEC_SYNCHRONOUS);
       else
+	set_cmdstat (cmdstat, EXEC_NOERROR);
+
+      if (res != -1)
 	{
-	  set_cmdstat (cmdstat, 0);
 #if defined(WEXITSTATUS) && defined(WIFEXITED)
 	  *exitstat = WIFEXITED(res) ? WEXITSTATUS(res) : res;
 #else
@@ -107,7 +112,7 @@ execute_command_line (const char *command, bool wait, int *exitstat,
     }
 
   /* Now copy back to the Fortran string if needed.  */
-  if (cmdstat && *cmdstat > 0)
+  if (cmdstat && *cmdstat > EXEC_NOERROR)
     {
       if (cmdmsg)
 	fstrcpy (cmdmsg, cmdmsg_len, cmdmsg_values[*cmdstat],