Fix save/restore of errno for isatty().

src/coloredstderr.c

@@ -64,6 +64,19 @@ static int force_write_to_non_tty;
 /* See hookmacros.h for the decision if a function call is colored. */
 
 
+/* Prevent inlining into hook functions because it may increase the number of
+ * spilled registers unnecessarily. As it's not called very often accept the
+ * additional call. */
+static int isatty_noinline(int fd) __noinline;
+static int isatty_noinline(int fd) {
+    int saved_errno = errno;
+    int result = isatty(fd);
+    errno = saved_errno;
+
+    return result;
+}
+
+
 static void dup_fd(int oldfd, int newfd) {
 #ifdef DEBUG
     debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());

src/hookmacros.h

@@ -38,7 +38,7 @@
  *         if (force_write_to_non_tty) {
  *             handle = 1;
  *         } else {
- *             handle = isatty(<fd>);
+ *             handle = isatty_noinline(<fd>);
  *         }
  *     } else {
  *         handle = 0;
@@ -72,7 +72,7 @@
             if (unlikely(force_write_to_non_tty)) { \
                 handle = 1; \
             } else { \
-                handle = isatty(fd); \
+                handle = isatty_noinline(fd); \
             } \
         } else { \
             handle = 0; \
@@ -87,7 +87,7 @@
             if (unlikely(force_write_to_non_tty)) { \
                 handle = 1; \
             } else { \
-                handle = isatty(fileno(file)); \
+                handle = isatty_noinline(fileno(file)); \
             } \
         } else { \
             handle = 0; \