Remove errno save/restore where not necessary.

src/coloredstderr.c

@@ -75,11 +75,15 @@ static int check_handle_fd(int fd) {
 
     /* Never touch anything not going to a terminal - unless we are explicitly
      * asked to do so. */
-    if (!force_write_to_non_tty && !isatty(fd)) {
-        return 0;
+    if (force_write_to_non_tty) {
+        return 1;
     }
 
-    return 1;
+    int saved_errno = errno;
+    int result = isatty(fd);
+    errno = saved_errno;
+
+    return result;
 }
 
 static void dup_fd(int oldfd, int newfd) {
@@ -141,29 +145,45 @@ inline static void init_pre_post_string(void) {
 }
 
 static void handle_fd_pre(int fd) {
+    int saved_errno = errno;
+
     if (!pre_string || !post_string) {
         init_pre_post_string();
     }
 
     DLSYM_FUNCTION(real_write, "write");
     real_write(fd, pre_string, pre_string_size);
+
+    errno = saved_errno;
 }
 static void handle_fd_post(int fd) {
+    int saved_errno = errno;
+
     /* write() already loaded above in handle_fd_pre(). */
     real_write(fd, post_string, post_string_size);
+
+    errno = saved_errno;
 }
 
 static void handle_file_pre(FILE *stream) {
+    int saved_errno = errno;
+
     if (!pre_string || !post_string) {
         init_pre_post_string();
     }
 
     DLSYM_FUNCTION(real_fwrite, "fwrite");
     real_fwrite(pre_string, pre_string_size, 1, stream);
+
+    errno = saved_errno;
 }
 static void handle_file_post(FILE *stream) {
+    int saved_errno = errno;
+
     /* fwrite() already loaded above in handle_file_pre(). */
     real_fwrite(post_string, post_string_size, 1, stream);
+
+    errno = saved_errno;
 }
 
 
@@ -303,9 +323,7 @@ int dup(int oldfd) {
 
     newfd = real_dup(oldfd);
     if (newfd != -1) {
-        int saved_errno = errno;
         dup_fd(oldfd, newfd);
-        errno = saved_errno;
     }
 
     return newfd;
@@ -315,9 +333,7 @@ int dup2(int oldfd, int newfd) {
 
     newfd = real_dup2(oldfd, newfd);
     if (newfd != -1) {
-        int saved_errno = errno;
         dup_fd(oldfd, newfd);
-        errno = saved_errno;
     }
 
     return newfd;
@@ -327,9 +343,7 @@ int dup3(int oldfd, int newfd, int flags) {
 
     newfd = real_dup3(oldfd, newfd, flags);
     if (newfd != -1) {
-        int saved_errno = errno;
         dup_fd(oldfd, newfd);
-        errno = saved_errno;
     }
 
     return newfd;
@@ -361,9 +375,7 @@ int fcntl(int fd, int cmd, ...) {
 
     /* We only care about duping fds. */
     if (cmd == F_DUPFD && result != -1) {
-        int saved_errno = errno;
         dup_fd(fd, result);
-        errno = saved_errno;
     }
 
     return result;

src/debug.h

@@ -44,10 +44,13 @@ static void debug_write(int fd, int first_call, char const *format, va_list ap)
 static void debug(char const *format, ...) {
     va_list ap;
 
+    int saved_errno = errno;
+
     /* If the file doesn't exist, do nothing. Prevents writing log files in
      * unexpected places. The user must create the file manually. */
     int fd = open(DEBUG_FILE, O_WRONLY | O_APPEND);
     if (fd == -1) {
+        errno = saved_errno;
         return;
     }
 
@@ -57,13 +60,18 @@ static void debug(char const *format, ...) {
     va_start(ap, format);
     debug_write(fd, call_count == 1, format, ap);
     va_end(ap);
+
+    errno = saved_errno;
 }
 
 static void warning(char const *format, ...) {
     va_list ap;
 
+    int saved_errno = errno;
+
     char const *home = getenv("HOME");
     if (!home) {
+        errno = saved_errno;
         return;
     }
 
@@ -75,6 +83,7 @@ static void warning(char const *format, ...) {
     /* Create the warning file if it doesn't exist yet. */
     int fd = open(path, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
     if (fd == -1) {
+        errno = saved_errno;
         return;
     }
 
@@ -84,6 +93,8 @@ static void warning(char const *format, ...) {
     va_start(ap, format);
     debug_write(fd, call_count == 1, format, ap);
     va_end(ap);
+
+    errno = saved_errno;
 }
 
 #endif

src/hookmacros.h

@@ -26,7 +26,6 @@
 
 #define _HOOK_PRE(type, name) \
         int handle; \
-        int saved_errno = errno; \
         DLSYM_FUNCTION(real_ ## name, #name);
 #define _HOOK_PRE_FD(type, name, fd) \
         type result; \
@@ -36,32 +35,24 @@
         handle = check_handle_fd(fd); \
         if (handle) { \
             handle_fd_pre(fd); \
-        } \
-        errno = saved_errno;
+        }
 #define _HOOK_PRE_FILE(type, name, file) \
         type result; \
         _HOOK_PRE(type, name) \
         handle = check_handle_fd(fileno(file)); \
         if (handle) { \
             handle_file_pre(file); \
-        } \
-        errno = saved_errno;
-/* Save and restore the errno to make sure we return the errno of the original
- * function call. */
+        }
 #define _HOOK_POST_FD_(fd) \
         if (handle) { \
-            saved_errno = errno; \
             handle_fd_post(fd); \
-            errno = saved_errno; \
         }
 #define _HOOK_POST_FD(fd) \
         _HOOK_POST_FD_(fd) \
         return result;
 #define _HOOK_POST_FILE(file) \
         if (handle) { \
-            saved_errno = errno; \
             handle_file_post(file); \
-            errno = saved_errno; \
         } \
         return result;
 

src/ldpreload.h

@@ -34,6 +34,7 @@
  * Terminate program on failure. */
 #define DLSYM_FUNCTION(pointer, name) \
     if (NULL == (pointer)) { \
+        int saved_errnox = errno; \
         char *error; \
         dlerror(); /* Clear possibly existing error. */ \
         \
@@ -44,6 +45,7 @@
              * failed to load too. */ \
             abort(); \
         } \
+        errno = saved_errnox; \
     }
 
 #endif

src/trackfds.h

@@ -78,6 +78,8 @@ static void init_from_environment(void) {
 #endif
     char const *env;
 
+    int saved_errno = errno;
+
     initialized = 1;
     tracked_fds_list_count = 0;
 
@@ -90,6 +92,7 @@ static void init_from_environment(void) {
 
     env = getenv(ENV_NAME_FDS);
     if (!env) {
+        errno = saved_errno;
         return;
     }
     /* Environment is read-only. */
@@ -153,6 +156,8 @@ next:
 #ifdef DEBUG
     tracked_fds_debug();
 #endif
+
+    errno = saved_errno;
 }
 
 static char *update_environment_buffer_entry(char *x, int fd) {
@@ -231,6 +236,8 @@ static void tracked_fds_add(int fd) {
     }
 
     if (tracked_fds_list_count >= tracked_fds_list_space) {
+        int saved_errno = errno;
+
         size_t new_space = tracked_fds_list_space + TRACKFDS_REALLOC_STEP;
         int *tmp = realloc(tracked_fds_list,
                            sizeof(*tracked_fds_list) * new_space);
@@ -242,8 +249,11 @@ static void tracked_fds_add(int fd) {
             warning("realloc(tracked_fds_list, %zu) failed! [%d]\n",
                     sizeof(*tracked_fds_list) * new_space, getpid());
 #endif
+            errno = saved_errno;
             return;
         }
+        errno = saved_errno;
+
         tracked_fds_list = tmp;
         tracked_fds_list_space = new_space;
     }