[PATCH 3/3] Delay closing the history file until the fcntl-lock is released.

[Philippe Troin <phil+github-commits@xxxxxxxx>]

Closes are not delayed if zsh is not compiled with fcntl() lock or if
the histfcntllock option isn't set.
---
 Src/hist.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 93 insertions(+), 4 deletions(-)

diff --git a/Src/hist.c b/Src/hist.c
index 981316674..2d0b3eb0f 100644
--- a/Src/hist.c
+++ b/Src/hist.c
@@ -2527,6 +2527,63 @@ readhistline(int start, char **bufp, int *bufsiz, FILE *in)
 
 #ifdef HAVE_FCNTL_H
 static int flock_fd = -1;
+#define FLOCK_MAX_FILES_TO_CLOSE 10
+static int flock_fds_to_close[FLOCK_MAX_FILES_TO_CLOSE] = { -1 };
+static FILE* flock_files_to_close[FLOCK_MAX_FILES_TO_CLOSE];
+
+static int
+closehistfd(int fd) {
+    int i;
+
+    if (flock_fd < 0) {
+	return close(fd);
+    }
+
+    for (i=0; i < FLOCK_MAX_FILES_TO_CLOSE; ++i) {
+	if (flock_fds_to_close[i] < 0) {
+	    break;
+	}
+    }
+
+    if (i >= FLOCK_MAX_FILES_TO_CLOSE) {
+	zerr("Ran out of flock_fds_to_close, increase the "
+	     "FLOCK_MAX_FILES_TO_CLOSE limit (currently at %d) in hist.c.",
+	     FLOCK_MAX_FILES_TO_CLOSE);
+	/* Close if we can't postpone */
+	return close(fd);
+    }
+
+    flock_fds_to_close[i] = fd;
+
+    return 0;
+}
+
+static int
+closehistfile(FILE* fp) {
+    int i;
+
+    if (flock_fd < 0) {
+	return fclose(fp);
+    }
+
+    for (i=0; i < FLOCK_MAX_FILES_TO_CLOSE; ++i) {
+	if (! flock_files_to_close[i]) {
+	    break;
+	}
+    }
+
+    if (i >= FLOCK_MAX_FILES_TO_CLOSE) {
+	zerr("Ran out of flock_files_to_close, increase the "
+	     "FLOCK_MAX_FILES_TO_CLOSE limit (currently at %d) in hist.c.",
+	     FLOCK_MAX_FILES_TO_CLOSE);
+	/* Close if we can't postpone */
+	return fclose(fp);
+    }
+
+    flock_files_to_close[i] = fp;
+
+    return 0;
+}
 
 /*
  * Lock file using fcntl().  Return 0 on success, 1 on failure of
@@ -2539,10 +2596,18 @@ flockhistfile(char *fn, int keep_trying)
     struct flock lck;
     long sleep_us = 0x10000; /* about 67 ms */
     time_t end_time;
+    int i;
 
     if (flock_fd >= 0)
 	return 0; /* already locked */
 
+    /* Clear out the list of fds/file descriptors which will be closed
+       upon relinquising the lock */
+    memset(flock_files_to_close, 0, sizeof(flock_files_to_close[0])*FLOCK_MAX_FILES_TO_CLOSE);
+    for (i=0; i < FLOCK_MAX_FILES_TO_CLOSE; ++i) {
+	flock_fds_to_close[i] = -1;
+    }
+
     if ((flock_fd = open(unmeta(fn), O_RDWR | O_NOCTTY)) < 0)
 	return errno == ENOENT ? 0 : 2; /* "successfully" locked missing file */
 
@@ -2575,12 +2640,36 @@ flockhistfile(char *fn, int keep_trying)
 static void
 funlockhistfile()
 {
+    int i;
+
     if (flock_fd >= 0) {
 	close(flock_fd);
 	flock_fd = -1;
     }
+
+    for (i=0; i < FLOCK_MAX_FILES_TO_CLOSE; ++i) {
+	if (flock_files_to_close[i]) {
+	    fclose(flock_files_to_close[i]);
+	    flock_files_to_close[i] = NULL;
+	} else {
+	    break;
+	}
+    }
+
+    for (i=0; i < FLOCK_MAX_FILES_TO_CLOSE; ++i) {
+	if (flock_fds_to_close[i] >= 0) {
+	    close(flock_fds_to_close[i]);
+	    flock_fds_to_close[i] = -1;
+	} else {
+	    break;
+	}
+    }
 }
-#endif
+
+#else /* ! HAVE_FCNTL_H */
+#  define closehistfd(x)   close(x)
+#  define closehistfile(x) fclose(x)
+#endif /* ! HAVE_FCNTL_H */
 
 /**/
 void
@@ -2768,7 +2857,7 @@ readhistfile(char *fn, int err, int readflags)
 	zfree(buf, bufsiz);
 
 	popheap();
-	fclose(in);
+	closehistfile(in);
     } else if (err)
 	zerr("can't read history file %s", fn);
 
@@ -2860,7 +2949,7 @@ savehistfile(char *fn, int err, int writeflags)
 		if (fd >=0) {
 		    out = fdopen(fd, "w");
 		    if (!out)
-			close(fd);
+			closehistfd(fd);
 		} else
 		    out = NULL;
 	    }
@@ -2948,7 +3037,7 @@ savehistfile(char *fn, int err, int writeflags)
 		lasthist.text = ztrdup(start);
 	    }
 	}
-	if (fclose(out) < 0 && ret >= 0)
+	if (closehistfile(out) < 0 && ret >= 0)
 	    ret = -1;
 	if (ret >= 0) {
 	    if (tmpfile) {
-- 
2.20.1