execute: Treat signalled processes like wait-process does

[Bruno Haible]

When a child process terminates through a signal, the convention in posix_spawn
is that the parent process sees an exit code of 127. This convention should
also hold for the 'execute' module. On native Windows, this requires mapping
the exit code 3 (from Microsoft) to exit code 127 (per POSIX).


2020-12-24  Bruno Haible  <br...@clisp.org>

        execute: Treat signalled processes like wait-process does.
        * lib/execute.c: Include <sys/types.h>, <sys/wait.h>.
        (execute): Recognize the case where the exit code indicates a signalled
        child process.
        * tests/test-execute-main.c (main): Update expected test result.
        * modules/execute (Depends-on): Add sys_wait.

diff --git a/lib/execute.c b/lib/execute.c
index 38dd07b..4cc779e 100644
--- a/lib/execute.c
+++ b/lib/execute.c
@@ -28,6 +28,9 @@
 #include <signal.h>
 #include <unistd.h>
 
+#include <sys/types.h>
+#include <sys/wait.h>
+
 #include "canonicalize.h"
 #include "error.h"
 #include "fatal-signal.h"
@@ -214,12 +217,22 @@ execute (const char *progname,
   free (argv_mem_to_free);
   free (prog_path_to_free);
 
+  /* Treat failure and signalled child processes like wait_subprocess()
+     does.  */
   if (termsigp != NULL)
     *termsigp = 0;
 
   if (exitcode == -1)
     goto fail_with_saved_errno;
 
+  if (WIFSIGNALED (exitcode))
+    {
+      if (termsigp != NULL)
+        *termsigp = WTERMSIG (exitcode);
+      saved_errno = 0;
+      goto fail_with_saved_errno;
+    }
+
   return exitcode;
 
 #else
diff --git a/modules/execute b/modules/execute
index 90a7b89..4345580 100644
--- a/modules/execute
+++ b/modules/execute
@@ -29,6 +29,7 @@ posix_spawnattr_setflags
 posix_spawnattr_destroy
 stdbool
 stdlib
+sys_wait
 unistd
 wait-process
 windows-spawn
diff --git a/tests/test-execute-main.c b/tests/test-execute-main.c
index c58a62d..29a4c30 100644
--- a/tests/test-execute-main.c
+++ b/tests/test-execute-main.c
@@ -135,11 +135,10 @@ main (int argc, char *argv[])
         int termsig = 0xDEADBEEF;
         int ret = execute (progname, prog_argv[0], prog_argv, NULL,
                            false, false, false, false, true, false, &termsig);
+        ASSERT (ret == 127);
         #if defined _WIN32 && !defined __CYGWIN__
-        ASSERT (ret == 3);
-        ASSERT (termsig == 0);
+        ASSERT (termsig == SIGTERM); /* dummy, from WTERMSIG in <sys/wait.h> */
         #else
-        ASSERT (ret == 127);
         ASSERT (termsig == SIGINT);
         #endif
       }