varlink: use two local flag variables to silence gcc warning

[59/655] Compiling C object src/shared/libsystemd-shared-248.a.p/varlink.c.o
../src/shared/varlink.c: In function ‘varlink_write’:
../src/shared/varlink.c:459:12: warning: ‘n’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  459 |         if (n < 0) {
      |            ^
../src/shared/varlink.c: In function ‘varlink_process’:
../src/shared/varlink.c:541:12: warning: ‘n’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  541 |         if (n < 0) {
      |            ^
../src/shared/varlink.c:486:17: note: ‘n’ was declared here
  486 |         ssize_t n;
      |                 ^

diff --git a/src/shared/varlink.c b/src/shared/varlink.c
index 6ed72075ba5beda6ac98bb2dbcaad0f96c19fcd4..a271082ac33a9dca7c05e37c37919e2bda9839ac 100644 (file)
--- a/src/shared/varlink.c
+++ b/src/shared/varlink.c
@@ -448,13 +448,16 @@ static int varlink_write(Varlink *v) {
         assert(v->fd >= 0);
 
         /* We generally prefer recv()/send() (mostly because of MSG_NOSIGNAL) but also want to be compatible
-         * with non-socket IO, hence fall back automatically */
-        if (!v->prefer_read_write) {
+         * with non-socket IO, hence fall back automatically.
+         *
+         * Use a local variable to help gcc figure out that we set 'n' in all cases. */
+        bool prefer_write = v->prefer_read_write;
+        if (!prefer_write) {
                 n = send(v->fd, v->output_buffer + v->output_buffer_index, v->output_buffer_size, MSG_DONTWAIT|MSG_NOSIGNAL);
                 if (n < 0 && errno == ENOTSOCK)
-                        v->prefer_read_write = true;
+                        prefer_write = v->prefer_read_write = true;
         }
-        if (v->prefer_read_write)
+        if (prefer_write)
                 n = write(v->fd, v->output_buffer + v->output_buffer_index, v->output_buffer_size);
         if (n < 0) {
                 if (errno == EAGAIN)
@@ -531,12 +534,13 @@ static int varlink_read(Varlink *v) {
 
         rs = v->input_buffer_allocated - (v->input_buffer_index + v->input_buffer_size);
 
-        if (!v->prefer_read_write) {
+        bool prefer_read = v->prefer_read_write;
+        if (!prefer_read) {
                 n = recv(v->fd, v->input_buffer + v->input_buffer_index + v->input_buffer_size, rs, MSG_DONTWAIT);
                 if (n < 0 && errno == ENOTSOCK)
-                        v->prefer_read_write = true;
+                        prefer_read = v->prefer_read_write = true;
         }
-        if (v->prefer_read_write)
+        if (prefer_read)
                 n = read(v->fd, v->input_buffer + v->input_buffer_index + v->input_buffer_size, rs);
         if (n < 0) {
                 if (errno == EAGAIN)