diff: fix small bug; don't make a copy for "/dev/null" case

diff --git a/editors/diff.c b/editors/diff.c
index 7a64225645b70327966be2280b4a90c9e91daa60..27c8365cc495a0214a20475a9f9b8ce21cb1c9fa 100644 (file)
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -283,7 +283,7 @@ static char *make_temp(FILE *f, struct stat *sb)
        char *name;
        int fd;
 
-       if (S_ISREG(sb->st_mode))
+       if (S_ISREG(sb->st_mode) || S_ISBLK(sb->st_mode))
                return NULL;
        name = xstrdup("/tmp/difXXXXXX");
        fd = mkstemp(name);
@@ -312,9 +312,15 @@ static NOINLINE int files_differ(FILE *f1, FILE *f2, int flags)
 {
        size_t i, j;
 
+       /* Prevent making copies for "/dev/null" (too common) */
+       tempname1 = tempname2 = NULL;
+       if (flags & (D_EMPTY1 | D_EMPTY2)) {
+               return 1;
+       }
+       /* Deal with input from pipes etc */
        tempname1 = make_temp(f1, &stb1);
        tempname2 = make_temp(f2, &stb2);
-       if ((flags & (D_EMPTY1 | D_EMPTY2)) || stb1.st_size != stb2.st_size) {
+       if (stb1.st_size != stb2.st_size) {
                return 1;
        }
        while (1) {
@@ -631,8 +637,8 @@ static NOINLINE void check(FILE *f1, FILE *f2)
                                        J[i] = 0;
                                        if (c != '\n' && c != EOF)
                                                ctold += skipline(f1);
-// BUG? Should be "if (d != '\n' && d != EOF)" ?
-                                       if (d != '\n' && c != EOF)
+/* was buggy? "if (d != '\n' && c != EOF)" */
+                                       if (d != '\n' && d != EOF)
                                                ctnew += skipline(f2);
                                        break;
                                }