Re: [patch] [gdb/testsuite] include a use of the definition of a type to cause clang to emit debug info

[David Blaikie <dblaikie@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1956 bytes --]

Oh, and there was one other instance of the same issue (I believe
these are the only two cases)

This test case (gdb.cp/pr10728) seems like it could probably be
simplified a great deal, down to:

struct foo;
foo *f, *g;
int main() {
} // break and print f - g

if I'm not mistaken... - but I've made a relatively small change for
now. If preferred, I can make the more substantial simplification
suggested. Or otherwise appease clang (by introducing a use of the
original 'x' type definition in some other way - dereferencing a
pointer, etc).

- David

On Sat, Apr 12, 2014 at 11:43 PM, David Blaikie <dblaikie@gmail.com> wrote:
> Clang has an optimization that causes a the debug info to only include
> the declaration of a type if the type is referenced but never used in
> a context that requires a definition (eg: pointers are handed around
> but never deferenced).
>
> This patch introduces a variable to one test file to cause clang to
> emit the full definition of the type as well as fixing up a related
> typo in the test message of the associated expect file.
>
> Like the difference between GCC and Clang in the emission of unused
> static entities, I think this case is also a matter of degrees - both
> GCC and Clang implement other similar optimizations* to the one
> outlined here and the GDB test suite has managed to pass without
> disabling those optimizations in GCC and I hope it's suitable to do
> the same for Clang.
>
> Though admittedly I don't have much of the context of the history of
> the testsuite, its priorities/preferences when it comes to
> distinguishing testing compiler behavior versus debugger behavior,
> etc.
>
> * the one I know of involves dynamic types: both GCC and Clang only
> emit the debug info definition of such a type in any translation unit
> that emits the key function. This means in many contexts where a full
> definition is provided in the source only a declaration is provided in
> the debug info.

[-- Attachment #2: pr10728-full-type.diff --]
[-- Type: text/plain, Size: 1812 bytes --]

commit 24a8810a97155710d3c53b401eb8729bc4f80c00
Author: David Blaikie <dblaikie@gmail.com>
Date:   Sun Apr 13 00:48:45 2014 -0700

    Return by value to coax Clang into emitting the full definition of a test type.
    
    gdb/testsuite/
    	* gdb.cp/pr10728-x.cc: Return by value instead of pointer to coax
    	Clang into emitting the definition of the type.
    	* gdb.cp/pr10728-x.h: Ditto.
    	* gdb.cp/pr10728-y.cc: Ditto.

diff --git gdb/testsuite/ChangeLog gdb/testsuite/ChangeLog
index 730c116..1d15721 100644
--- gdb/testsuite/ChangeLog
+++ gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2014-04-12  David Blaikie  <dblaikie@gmail.com>
+
+	* gdb.cp/pr10728-x.cc: Return by value instead of pointer to coax
+	Clang into emitting the definition of the type.
+	* gdb.cp/pr10728-x.h: Ditto.
+	* gdb.cp/pr10728-y.cc: Ditto.
+
 2014-04-12  Siva Chandra Reddy  <sivachandra@google.com>
 	    Doug Evans  <xdje42@gmail.com>
 
diff --git gdb/testsuite/gdb.cp/pr10728-x.cc gdb/testsuite/gdb.cp/pr10728-x.cc
index 7623c0b..d6b7666 100644
--- gdb/testsuite/gdb.cp/pr10728-x.cc
+++ gdb/testsuite/gdb.cp/pr10728-x.cc
@@ -2,6 +2,6 @@
 
 int main()
 {
-  X* x = y();
+  X x = y();
   return 0;		// marker 1
 }
diff --git gdb/testsuite/gdb.cp/pr10728-x.h gdb/testsuite/gdb.cp/pr10728-x.h
index 63737d9..0ba58bb 100644
--- gdb/testsuite/gdb.cp/pr10728-x.h
+++ gdb/testsuite/gdb.cp/pr10728-x.h
@@ -5,5 +5,5 @@ struct X
   Y* y2;
 };
 
-X* y();
+X y();
 
diff --git gdb/testsuite/gdb.cp/pr10728-y.cc gdb/testsuite/gdb.cp/pr10728-y.cc
index 84b222d..d8a932a 100644
--- gdb/testsuite/gdb.cp/pr10728-y.cc
+++ gdb/testsuite/gdb.cp/pr10728-y.cc
@@ -1,11 +1,11 @@
 #include "pr10728-x.h"
 struct Y{};
 
-X* y()
+X y()
 {
-  static X xx;
+  X xx;
   static Y yy;
   xx.y1 = &yy;
   xx.y2 = xx.y1+1;
-  return &xx;
+  return xx;
 }