[DebugInfo] Generate debug info for system typedefs even with -fno-sy…

…stem-debug

Signed-off-by: Lu, John <[email protected]>

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -6027,6 +6027,18 @@ bool clang::CodeGen::noSystemDebugInfo(const Decl *D,
                                        const CodeGenModule &CGM) {
   // Declaration is in system file
   if (CGM.getContext().getSourceManager().isInSystemHeader(D->getLocation())) {
+    // Make an exception for typedefs in system header files.  Generate debug
+    // information for these decls because these are rare (thus they will not
+    // greatly increase debug size) and a user could rely on these typedefs
+    // during debugging. For example uid_t in in "sys/types.h" can be used in
+    // the gdb command:
+    //
+    //    print ruid == (uid_t)-1
+    //
+    // This occurs in GDB test gdb.reverse/getresuid-reverse.c
+    if (isa<TypedefDecl>(D))
+      return false;
+
     // -fno-system-debug was used.  Do not generate debug info.
     if (CGM.getCodeGenOpts().NoSystemDebug)
       return true;

clang/test/CodeGen/debug-info-system-typedef.c

@@ -0,0 +1,25 @@
+// Ensure that debug info for typedefs in system headers is still generated
+// even if -fno-system-debug is used.  This is justified because debug size 
+// savings is small, but debugging is commonly done with types that are
+// typedef-ed in system headers.  Thus, the increased debuggability
+// is worth the small extra cost.
+
+// RUN: %clang -fno-system-debug -emit-llvm -S -g %s -o %t.ll
+
+// RUN: FileCheck %s < %t.ll
+
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "gid_t",
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "__gid_t",
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "uid_t",
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "__uid_t",
+
+#include <unistd.h>
+
+uid_t xuid;
+gid_t xgid;
+
+int
+main (void)
+{
+  return 0;
+}