[profile] Add llvm_gcov_flush to be called outside a shared library

__gcov_flush is hidden.
For applications to dump profiling data of selected .so files,
they can use dlsym to find and call llvm_gcov_flush in each .so file.

Differential Revision: https://reviews.llvm.org/D45454

llvm-svn: 336019

compiler-rt/lib/profile/GCDAProfiling.c

@@ -527,6 +527,10 @@ void llvm_register_flush_function(flush_fn fn) {
   }
 }
 
+// __gcov_flush is hidden. When called in a .so file,
+// it dumps profile data of the calling .so file.
+// If a main program needs to dump profile data of each linked
+// .so files, it should use dlsym to find and call llvm_gcov_flush.
 COMPILER_RT_VISIBILITY
 void __gcov_flush() {
   struct flush_fn_node *curr = flush_fn_head;
@@ -537,6 +541,12 @@ void __gcov_flush() {
   }
 }
 
+// llvm_gcov_flush is not hidden for a program to use dlsym to
+// find and call for any linked .so file.
+void llvm_gcov_flush() {
+  __gcov_flush();
+}
+
 COMPILER_RT_VISIBILITY
 void llvm_delete_flush_function_list(void) {
   while (flush_fn_head) {

compiler-rt/test/profile/Inputs/instrprof-dlopen-dlclose-main.c

@@ -10,12 +10,42 @@ int main(int argc, char *argv[]) {
     return EXIT_FAILURE;
   }
 
+  dlerror();
   void *f2_handle = dlopen("func2.shared", RTLD_LAZY | RTLD_GLOBAL);
   if (f2_handle == NULL) {
     fprintf(stderr, "unable to open 'func2.shared': %s\n", dlerror());
     return EXIT_FAILURE;
   }
 
+  dlerror();
+  void (*gcov_flush)() = (void (*)())dlsym(f1_handle, "__gcov_flush");
+  if (gcov_flush != NULL || dlerror() == NULL) {
+    fprintf(stderr, "__gcov_flush should not be visible in func.shared'\n");
+    return EXIT_FAILURE;
+  }
+
+  dlerror();
+  void (*f1_flush)() = (void (*)())dlsym(f1_handle, "llvm_gcov_flush");
+  if (f1_flush == NULL) {
+    fprintf(stderr, "unable to find llvm_gcov_flush in func.shared': %s\n", dlerror());
+    return EXIT_FAILURE;
+  }
+  f1_flush();
+
+  dlerror();
+  void (*f2_flush)() = (void (*)())dlsym(f2_handle, "llvm_gcov_flush");
+  if (f2_flush == NULL) {
+    fprintf(stderr, "unable to find llvm_gcov_flush in func2.shared': %s\n", dlerror());
+    return EXIT_FAILURE;
+  }
+  f2_flush();
+
+  if (f1_flush == f2_flush) {
+    fprintf(stderr, "Same llvm_gcov_flush found in func.shared and func2.shared\n");
+    return EXIT_FAILURE;
+  }
+
+  dlerror();
   if (dlclose(f2_handle) != 0) {
     fprintf(stderr, "unable to close 'func2.shared': %s\n", dlerror());
     return EXIT_FAILURE;