[patch] Add new warning -Wtrampolines

[Magnus Granberg <zorry at gentoo dot org>]

Hi

This patch add new warning -Wtrampolines for making the compile to warn when it 
generating trampoline in object that requires executable stack.
Tested on x86_64-unknown-linux-gnu and it have been in the Gentoo GCC patchset
for long time (2006).

Hardened at Gentoo.org
Magnus Granberg (Zorry) <zorry@gentoo.org>

gcc/

2010-05-06	Magnus Granberg		<zorry@gentoo.org>, Kevin F. Quinn <kevquinn@gentoo.org>

		* builtins.c (expand_builtin_init_trampoline):	if warn_trampolines make a warning.
		* common.opt:	Add -Wtrampolines.

gcc/doc

2010-05-06	Magnus Granberg		<zorry@gentoo.org>

		* invoke.texi:	Add -Wtrampolines.

gcc/testsuite/

2010-05-06	Magnus Granberg		<zorry@gentoo.org>

		* gcc.dg/Wtrampolines.c:	New.
---

--- gcc/builtins.c.zorry	2010-04-13 15:47:11.000000000 +0200
+++ gcc/builtins.c			2010-04-25 22:45:49.000000000 +0200
@@ -5150,6 +5150,10 @@
   targetm.calls.trampoline_init (m_tramp, t_func, r_chain);
 
   trampolines_created = 1;
+  
+  if (warn_trampolines)
+    warning (OPT_Wtrampolines, "generating trampoline in object (requires executable stack)");
+
   return const0_rtx;
 }
 
--- gcc/common.opt.zorry	2010-03-18 04:01:09.000000000 +0100
+++ gcc/common.opt			2010-05-06 00:44:18.000000000 +0200
@@ -192,6 +192,12 @@
 Common Var(warn_system_headers) Warning
 Do not suppress warnings from system headers
 
+
+Wtrampolines
+Common Var(warn_trampolines) Warnings
+Warn whenever a trampoline is generated
+
+
 Wtype-limits
 Common Var(warn_type_limits) Init(-1) Warning
 Warn if a comparison is always true or always false due to the limited range of the data type
--- gcc/doc/invoke.texi.zorry	2010-04-06 16:02:22.000000000 +0200
+++ gcc/doc/invoke.texi			2010-05-06 00:20:25.000000000 +0200
@@ -258,8 +258,8 @@
 -Wstrict-aliasing -Wstrict-aliasing=n @gol
 -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
 -Wswitch  -Wswitch-default  -Wswitch-enum -Wsync-nand @gol
--Wsystem-headers  -Wtrigraphs  -Wtype-limits  -Wundef  -Wuninitialized @gol
--Wunknown-pragmas  -Wno-pragmas @gol
+-Wsystem-headers  -Wtrampolines  -Wtrigraphs  -Wtype-limits  -Wundef @gol
+-Wuninitialized  -Wunknown-pragmas  -Wno-pragmas @gol
 -Wunsuffixed-float-constants  -Wunused  -Wunused-function @gol
 -Wunused-label  -Wunused-parameter -Wno-unused-result -Wunused-value  -Wunused-variable @gol
 -Wvariadic-macros -Wvla @gol
@@ -3603,6 +3603,12 @@
 option will @emph{not} warn about unknown pragmas in system
 headers---for that, @option{-Wunknown-pragmas} must also be used.
 
+@item -Wtrampolines
+@opindex Wtrampolines
+@opindex Wno-trampolines
+Make a warning when the compiler generating trampoline in object that
+requires executable stack.
+
 @item -Wfloat-equal
 @opindex Wfloat-equal
 @opindex Wno-float-equal
--- gcc/testsuite/gcc.dg/Wtrampolines.c.zorry	2010-05-05 12:53:11.000000000 +0200
+++ gcc/testsuite/gcc.dg/Wtrampolines.c			2010-05-06 00:26:05.000000000 +0200
@@ -0,0 +1,57 @@
+/* Origin: trampoline-1.c Waldek Hebisch <hebisch@math.uni.wroc.pl> */
+/* Ported to test -Wtrampolines Magnus Granberg <zorry@gentoo.org> */
+
+/* { dg-do compile } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-O2 -Wtrampolines" } */
+
+#ifndef NO_TRAMPOLINES
+
+/* This used to fail on various versions of Solaris 2 because the
+   trampoline couldn't be made executable.  */
+
+extern void abort(void);
+extern double fabs(double);
+
+void foo (void)
+{
+  const int correct[1100] = {1, 0, -2, 0, 1, 0, 1, -1, -10, -30, -67};
+  int i;
+
+  double x1 (void) {return 1; }
+  double x2 (void) {return -1;}
+  double x3 (void) {return -1;}
+  double x4 (void) {return 1; }
+  double x5 (void) {return 0; }
+
+  typedef double pfun(void);
+
+  double a (int k, pfun x1, pfun x2, pfun x3, pfun x4, pfun x5)		/* { dg-warning "requires executable stack" } */
+  {
+    double b (void)
+    {
+      k = k - 1;
+      return a (k, b, x1, x2, x3, x4 );
+    }
+
+    if (k <= 0)
+      return x4 () + x5 ();
+    else
+      return b ();
+  }
+
+  for (i=0; i<=10; i++)
+  {
+    if (fabs(a( i, x1, x2, x3, x4, x5 ) - correct [i]) > 0.1)
+      abort();
+  }
+}
+#endif
+
+int main (void)
+{
+#ifndef NO_TRAMPOLINES
+  foo ();
+#endif
+  return 0;
+}