[Tools] Added stdout protection during dlopen

[Issue] During dlopen libraries loads other libraries. If any library in
the chain generates some output to stdout, it corrupts the json file.
To prevent this problem, we add stdout redirect during dlopen operation.

[Verification] Code compiles without errors; plugins.json file is
properly generated.

Change-Id: Ic46e5f1b8d90b2de0ffe1065f2fffaa75127de19

diff --git a/src/tool/desc_gentool.cc b/src/tool/desc_gentool.cc
index 3b58e00..6166872 100644 (file)
--- a/src/tool/desc_gentool.cc
+++ b/src/tool/desc_gentool.cc
@@ -135,6 +135,27 @@ const void* get_interface(const char* name) {
   return NULL;
 }
 
+struct stream_info {
+  int fd;
+  fpos_t pos;
+};
+struct stream_info s_info;
+
+void stdout_to_null() {
+  fflush(stdout);
+  fgetpos(stdout, &(s_info.pos));
+  s_info.fd = dup(fileno(stdout));
+  freopen("/dev/null", "w", stdout);
+}
+
+void reset_stdout() {
+  fflush(stdout);
+  dup2(s_info.fd, fileno(stdout));
+  close(s_info.fd);
+  clearerr(stdout);
+  fsetpos(stdout, &(s_info.pos));
+}
+
 int main(int argc, char* argv[]) {
   if (argc < 3) {
     std::cerr << "Need tizen crosswalk path" << std::endl;
@@ -155,6 +176,9 @@ int main(int argc, char* argv[]) {
   struct dirent** namelist;
   int num_entries = scandir(tec_path.c_str(), &namelist, NULL, alphasort);
   if (num_entries >= 0) {
+    // protect stdout for any unexpected text which can be printed by other
+    // libraries during dlopen
+    stdout_to_null();
     for (int i = 0; i < num_entries; ++i) {
       std::string fname = namelist[i]->d_name;
 
@@ -196,6 +220,8 @@ int main(int argc, char* argv[]) {
       free(namelist[i]);
     }
     free(namelist);
+    // reset stdout to previous values
+    reset_stdout();
     print_json();
   } else {
     perror("scandir");