From 957315035a5729ee089404fbdb2710fa78dca188 Mon Sep 17 00:00:00 2001
From: Frank Denis <github@pureftpd.org>
Date: Fri, 20 Jun 2014 21:09:18 -0700
Subject: [PATCH] Use weak symbols to prevent LTO if this is an option. Idea
 from Matthew Dempsky.

---
 configure.ac                 | 10 ++++++++++
 src/libsodium/sodium/utils.c |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/configure.ac b/configure.ac
index 6dd1346f..5bb01b87 100644
--- a/configure.ac
+++ b/configure.ac
@@ -375,6 +375,16 @@ __asm__ __volatile__ ("xchgl %%ebx, %k1; cpuid; xchgl %%ebx, %k1" :
   ])
 AC_SUBST(HAVE_CPUID_V)
 
+AC_MSG_CHECKING(if weak symbols are supported)
+AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+__attribute__((weak)) void __dummy(void *x) { }
+void f(void *x) { __dummy(x); }
+]], [[ ]]
+)],
+[AC_MSG_RESULT(yes)
+ AC_DEFINE([HAVE_WEAK_SYMBOLS], [1], [weak symbols are supported])],
+[AC_MSG_RESULT(no)])
+
 AS_CASE([$host_cpu],
   [i*86 | x86_64 | powerpc* | s390*],
     [AC_MSG_NOTICE([data alignment is not required on this target])],
diff --git a/src/libsodium/sodium/utils.c b/src/libsodium/sodium/utils.c
index e60bcd80..fbccfbb5 100644
--- a/src/libsodium/sodium/utils.c
+++ b/src/libsodium/sodium/utils.c
@@ -19,6 +19,11 @@
 # include <wincrypt.h>
 #endif
 
+#ifdef HAVE_WEAK_SYMBOLS
+__attribute__((weak)) void
+__sodium_dummy_symbol_to_prevent_lto(void * const pnt, const size_t len) { }
+#endif
+
 void
 sodium_memzero(void * const pnt, const size_t len)
 {
@@ -30,6 +35,9 @@ sodium_memzero(void * const pnt, const size_t len)
     }
 #elif defined(HAVE_EXPLICIT_BZERO)
     explicit_bzero(pnt, len);
+#elif HAVE_WEAK_SYMBOLS
+    memset(pnt, 0, len);
+    __sodium_dummy_symbol_to_prevent_lto(pnt, len);
 #else
     volatile unsigned char *pnt_ = (volatile unsigned char *) pnt;
     size_t                     i = (size_t) 0U;