setting error exit code when exec* errors (#65)

* setting error exit code when exec* errors

otherwise when exec* would fail, its the error is indicated by errno
however no appropriate exit code would be set and the overall subprocess
would be marked as successful with exit code of 0

* exec* never returns so always exiting without checking return value

* docs: add TODO to switch to abort()

nimutils/c/subproc.c

@@ -409,9 +409,16 @@ subproc_do_exec(subprocess_t *ctx)
     else {
         execv(ctx->cmd, ctx->argv);
     }
-    // If we get past the exec, kill the subproc, which will
-    // tear down the switchboard.
-    abort();
+    // If we get past the exec, kill the subproc with non-zero exit code,
+    // which will tear down the switchboard and print to stderr the
+    // errono description. For example for nonexisting command will be:
+    // foo: No such file or directory
+    fprintf(stderr, "%s: %s\n",ctx->cmd, strerror(errno));
+    // TODO switch back to abort() once better event handling is implemented
+    // in switchboard to correctly detect exit code as otherwise waitpid()
+    // detects program has exited however not all signal handlers have executed
+    // hence exit code is unknown yet
+    exit(1);
 }
 
 party_t *