[gPXE-devel] [PATCH] [compiler] Mark weak functions noinline

[Stefan Hajnoczi]

Weak functions whose visibility is hidden may be inlined due to a bug in
GCC.  Explicitly mark weak functions noinline to work around the
problem.

This makes the PXE_MENU config option work again, the PXE boot menu was
never being called because the compiler inlined a weak stub function.

The GCC bug was identified and fixed by Richard Sandiford
<rdsandiford at googlemail.com> but in the meantime gPXE needs to implement
a workaround.

Reported-by: Steve Jones <steve at squaregoldfish.co.uk>
Reported-by: Shao Miller <shao.miller at yrdsb.edu.on.ca>
Suggested-by: Joshua Oreman <oremanj at rwcr.net>
Signed-off-by: Stefan Hajnoczi <stefanha at gmail.com>
---
 src/include/compiler.h |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/include/compiler.h b/src/include/compiler.h
index 8ccc69c..926308b 100644
--- a/src/include/compiler.h
+++ b/src/include/compiler.h
@@ -181,8 +181,14 @@ REQUEST_EXPANDED ( CONFIG_SYMBOL );
 
 #ifndef ASSEMBLY
 
-/** Declare a function as weak (use *before* the definition) */
-#define __weak		__attribute__ (( weak ))
+/** Declare a function as weak (use *before* the definition)
+ *
+ * Due to a bug in at least GCC 4.4.4 and earlier, weak symbols may be inlined
+ * if they have hidden visibility (see above for why hidden visibility is
+ * used).  This results in the non-weak symbol never being used, so explicitly
+ * mark the function as noinline to prevent inlining.
+ */
+#define __weak		__attribute__ (( weak )) __attribute (( noinline ))
 
 #endif
 
-- 
1.7.1