[PATCH] Fix "Wait: No Child Process"

[PATCH] Fix "Wait: No Child Process"

[Baptiste Daroussin]

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Hi,

Here is a small patch to fix mandoc complaining about no child process when .gz
manpages are being read.

Best regards,
Bapt

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Index: read.c
===================================================================
RCS file: /cvs/mdocml/read.c,v
retrieving revision 1.128
diff -u -r1.128 read.c
--- read.c	23 Feb 2015 13:31:04 -0000	1.128
+++ read.c	2 Mar 2015 10:50:12 -0000
@@ -878,6 +878,7 @@
 		    "gunzip failed with code %d", WEXITSTATUS(status));
 		return(MANDOCLEVEL_ERROR);
 	}
+	curp->child = 0;
 	return(MANDOCLEVEL_OK);
 }
 

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Re: [PATCH] Fix "Wait: No Child Process"

[Ingo Schwarze]

Hi Baptiste,

Baptiste Daroussin wrote on Mon, Mar 02, 2015 at 11:55:19AM +0100:

> Here is a small patch to fix mandoc complaining about no child process
> when .gz manpages are being read.

Good catch, thanks for reporting!

I committed a tweaked version of the patch such that it also works
correctly if gunzip fails or is killed by a signal.

Yours,
  Ingo


> Index: read.c
> ===================================================================
> RCS file: /cvs/mdocml/read.c,v
> retrieving revision 1.128
> diff -u -r1.128 read.c
> --- read.c	23 Feb 2015 13:31:04 -0000	1.128
> +++ read.c	2 Mar 2015 10:50:12 -0000
> @@ -878,6 +878,7 @@
>  		    "gunzip failed with code %d", WEXITSTATUS(status));
>  		return(MANDOCLEVEL_ERROR);
>  	}
> +	curp->child = 0;
>  	return(MANDOCLEVEL_OK);
>  }
>  


Log Message:
-----------
If a non-gz manual is read after a gzipped manual, refrain 
from throwing a bogus error "wait: No child processes".
As reported by Baptiste Daroussin <bapt at FreeBSD dot org>, 
clearing the state variable curp->child after use was forgotten.

Modified Files:
--------------
    mdocml:
        read.c

Revision Data
-------------
Index: read.c
===================================================================
RCS file: /home/cvs/mdocml/mdocml/read.c,v
retrieving revision 1.128
retrieving revision 1.129
diff -Lread.c -Lread.c -u -p -r1.128 -r1.129
--- read.c
+++ read.c
@@ -868,6 +868,7 @@ mparse_wait(struct mparse *curp)
 		perror("wait");
 		exit((int)MANDOCLEVEL_SYSERR);
 	}
+	curp->child = 0;
 	if (WIFSIGNALED(status)) {
 		mandoc_vmsg(MANDOCERR_FILE, curp, 0, 0,
 		    "gunzip died from signal %d", WTERMSIG(status));
--
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Re: [PATCH] Fix "Wait: No Child Process"

[Kristaps Dzonsons]

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I'm still getting this error on Mac OS X, only for gzip'd files when
invoked as man(1).  Invoking directly as mandoc(1) does not cause the
issue.
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--
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Re: [PATCH] Fix "Wait: No Child Process"

[Ingo Schwarze]

Hi Kristaps,

Kristaps Dzonsons wrote on Mon, Mar 09, 2015 at 10:04:58PM +0100:

> I'm still getting this error on Mac OS X, only for gzip'd files
> when invoked as man(1).  Invoking directly as mandoc(1) does not
> cause the issue.

Gah, there was indeed a second issue causing this symptom, unrelated
to the one reported by bapt@.  It was introduced as a side effect of
main.c rev. 1.212 ("do not spawn a pager when there is no output").

Fixed now...

Thanks for reporting,
  Ingo


Log Message:
-----------
Fix a regression caused in rev. 1.212, reported by kristaps@:

When using a pager and the first manual shown is gzip'ed,
the gunzip(1) process ended up as a child of the pager process
such that the man(1) process couldn't wait for it, preventing
proper display of the manual.

Solve this by making the pager a child of the man(1) process
(instead of the other way round), which requires being a bit
more careful about properly closing file descriptors after use
and waiting for the pager before exiting man(1).

Modified Files:
--------------
    mdocml:
        main.c

Revision Data
-------------
Index: main.c
===================================================================
RCS file: /home/cvs/mdocml/mdocml/main.c,v
retrieving revision 1.223
retrieving revision 1.224
diff -Lmain.c -Lmain.c -u -p -r1.223 -r1.224
--- main.c
+++ main.c
@@ -20,6 +20,7 @@
 
 #include <sys/types.h>
 #include <sys/param.h>	/* MACHINE */
+#include <sys/wait.h>
 
 #include <assert.h>
 #include <ctype.h>
@@ -481,6 +482,21 @@ out:
 
 	free(defos);
 
+	/*
+	 * Flush the output and signal end of file.
+	 * If a pager is attached, it allows browsing to the end.
+	 * Otherwise, it does no harm, we are about to exit anyway.
+	 */
+
+	fclose(stdout);
+
+	/*
+	 * If we spawned a pager, wait for the user to close it.
+	 * Otherwise, this call fails with no adverse effect.
+	 */
+
+	wait(NULL);
+
 	return((int)rc);
 }
 
@@ -951,18 +967,19 @@ spawn_pager(void)
 		    progname, strerror(errno));
 		exit((int)MANDOCLEVEL_SYSERR);
 	case 0:
+		break;
+	default:
 		close(fildes[0]);
 		if (dup2(fildes[1], STDOUT_FILENO) == -1) {
 			fprintf(stderr, "%s: dup output: %s\n",
 			    progname, strerror(errno));
 			exit((int)MANDOCLEVEL_SYSERR);
 		}
+		close(fildes[1]);
 		return;
-	default:
-		break;
 	}
 
-	/* The original process becomes the pager. */
+	/* The child process becomes the pager. */
 
 	close(fildes[1]);
 	if (dup2(fildes[0], STDIN_FILENO) == -1) {
@@ -970,6 +987,7 @@ spawn_pager(void)
 		    progname, strerror(errno));
 		exit((int)MANDOCLEVEL_SYSERR);
 	}
+	close(fildes[0]);
 
 	pager = getenv("MANPAGER");
 	if (pager == NULL || *pager == '\0')
--
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