[PATCH] diff.c: clean temporary files

When diff-cache -p and friends are interrupted, they can leave
their temporary files behind.  Also when the external diff
program is killed instead of exiting (this usually happens when
piping the output to a pager, which can cause SIGPIPE when the
user quits viewing the diff early), they incorrectly died
without cleaning their temporary file.

This fixes these problems.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/diff.c b/diff.c
index c064e10580d5e1f7185f3f32ee19319292f6b43d..8659e4b04d46cb49e324d0a9fe05a0624e6ce4d3 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -3,6 +3,7 @@
  */
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <signal.h>
 #include "cache.h"
 #include "diff.h"
 
@@ -135,6 +136,9 @@ static void prepare_temp_file(const char *name,
 
        if (!one->file_valid) {
        not_a_valid_file:
+               /* A '-' entry produces this for file-2, and
+                * a '+' entry produces this for file-1.
+                */
                temp->name = "/dev/null";
                strcpy(temp->hex, ".");
                strcpy(temp->mode, ".");
@@ -155,7 +159,7 @@ static void prepare_temp_file(const char *name,
                                goto not_a_valid_file;
                        die("stat(%s): %s", temp->name, strerror(errno));
                }
-               strcpy(temp->hex, ".");
+               strcpy(temp->hex, sha1_to_hex(null_sha1));
                sprintf(temp->mode, "%06o",
                        S_IFREG |ce_permissions(st.st_mode));
        }
@@ -196,6 +200,11 @@ static void remove_tempfile(void)
                }
 }
 
+static void remove_tempfile_on_signal(int signo)
+{
+       remove_tempfile();
+}
+
 /* An external diff command takes:
  *
  * diff-cmd name infile1 infile1-sha1 infile1-mode \
@@ -207,7 +216,8 @@ void run_external_diff(const char *name,
                       struct diff_spec *two)
 {
        struct diff_tempfile *temp = diff_temp;
-       int pid, status;
+       pid_t pid;
+       int status;
        static int atexit_asked = 0;
 
        if (one && two) {
@@ -219,6 +229,7 @@ void run_external_diff(const char *name,
                        atexit_asked = 1;
                        atexit(remove_tempfile);
                }
+               signal(SIGINT, remove_tempfile_on_signal);
        }
 
        fflush(NULL);
@@ -246,9 +257,17 @@ void run_external_diff(const char *name,
                        printf("* Unmerged path %s\n", name);
                exit(0);
        }
-       if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status))
-               die("diff program failed");
-
+       if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status)) {
+               /* We do not check the exit status because typically
+                * diff exits non-zero if files are different, and
+                * we are not interested in knowing that.  We *knew*
+                * they are different and that's why we ran diff
+                * in the first place!  However if it dies by a signal,
+                * we stop processing immediately.
+                */
+               remove_tempfile();
+               die("external diff died unexpectedly.\n");
+       }
        remove_tempfile();
 }