Do not dump anonymous types from system headers

Fixes: diffblue#973

Author: stahlbauer

regression/goto-instrument/typedef4/main.c

@@ -0,0 +1,23 @@
+#ifndef _WIN32
+
+#include <signal.h>
+#include <stdlib.h>
+
+void sig_block(int sig)
+{
+  sigset_t ss;
+  sigemptyset(&ss);
+  sigaddset(&ss, sig);
+  sigprocmask(SIG_BLOCK, &ss, NULL);
+}
+
+int main() {
+  sig_block(0);
+  return 0;
+}
+#else
+int main()
+{
+  return 0;
+}
+#endif

regression/goto-instrument/typedef4/test.desc

@@ -0,0 +1,10 @@
+CORE
+main.c
+--dump-c --use-system-headers
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+--
+This test should be run via chain.sh, which will try to recompile the dumped C
+code. Missing/incomplete typedef output would cause a failure.

src/goto-instrument/dump_c.cpp

@@ -144,8 +144,9 @@ void dump_ct::operator()(std::ostream &os)
         symbol.type.set(ID_tag, new_tag);
     }
 
-    // we don't want to dump in full all definitions
-    if(!tag_added && ignore(symbol))
+    // we don't want to dump in full all definitions; in particular
+    // do not dump anonymous types that are defined in system headers
+    if((!tag_added || symbol.is_type) && ignore(symbol))
       continue;
 
     if(!symbols_sorted.insert(name_str).second)
@@ -1025,7 +1026,7 @@ void dump_ct::gather_global_typedefs()
   {
     const symbolt &symbol=symbol_entry.second;
 
-    if(symbol.is_macro && symbol.is_type && !ignore(symbol) &&
+    if(symbol.is_macro && symbol.is_type &&
        symbol.location.get_function().empty())
     {
       const irep_idt &typedef_str=symbol.type.get(ID_C_typedef);