From 95b9a477b6743004e0e9bf728b25bf63d2908777 Mon Sep 17 00:00:00 2001
From: Manuel Simoni <msimoni@gmail.com>
Date: Sat, 27 Feb 2010 17:37:59 +0100
Subject: [PATCH] weak function symbols

---
 examples/ex_weak.c | 11 +++++++++++
 examples/weak_f.c  |  6 ++++++
 libtcc.c           |  8 ++++++--
 tcc.h              |  4 +++-
 tccgen.c           |  4 ++++
 tcctok.h           |  2 ++
 6 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100755 examples/ex_weak.c
 create mode 100644 examples/weak_f.c

diff --git a/examples/ex_weak.c b/examples/ex_weak.c
new file mode 100755
index 00000000..2a2bd19c
--- /dev/null
+++ b/examples/ex_weak.c
@@ -0,0 +1,11 @@
+#! /usr/local/bin/tcc -run
+#include <tcclib.h>
+
+extern void weak_f (void) __attribute__ ((weak));
+
+int main ()
+{
+    if (weak_f) {
+        weak_f();
+    }
+}
diff --git a/examples/weak_f.c b/examples/weak_f.c
new file mode 100644
index 00000000..e7445317
--- /dev/null
+++ b/examples/weak_f.c
@@ -0,0 +1,6 @@
+#include <tcclib.h>
+
+void weak_f (void)
+{
+    printf("Weak\n");
+}
diff --git a/libtcc.c b/libtcc.c
index bea52de1..feb30bc1 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -424,8 +424,12 @@ ST_FUNC void put_extern_sym2(Sym *sym, Section *section,
 
     if (sym->type.t & VT_STATIC)
         sym_bind = STB_LOCAL;
-    else
-        sym_bind = STB_GLOBAL;
+    else {
+        if (FUNC_WEAK(sym->type.ref->r))
+            sym_bind = STB_WEAK;
+        else
+            sym_bind = STB_GLOBAL;
+    }
 
     if (!sym->c) {
         name = get_tok_str(sym->v, NULL);
diff --git a/tcc.h b/tcc.h
index 0170f11c..21cce75d 100644
--- a/tcc.h
+++ b/tcc.h
@@ -272,7 +272,8 @@ typedef struct AttributeDef {
       func_import   : 1,
       func_args     : 5,
       mode          : 4,
-      fill          : 12;
+      weak          : 1,
+      fill          : 11;
     struct Section *section;
 } AttributeDef;
 
@@ -283,6 +284,7 @@ typedef struct AttributeDef {
 #define FUNC_ARGS(r) (((AttributeDef*)&(r))->func_args)
 #define FUNC_ALIGN(r) (((AttributeDef*)&(r))->aligned)
 #define FUNC_PACKED(r) (((AttributeDef*)&(r))->packed)
+#define FUNC_WEAK(r) (((AttributeDef*)&(r))->weak)
 #define ATTR_MODE(r)  (((AttributeDef*)&(r))->mode)
 #define INT_ATTR(ad) (*(int*)(ad))
 
diff --git a/tccgen.c b/tccgen.c
index e761f917..805410b8 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -2462,6 +2462,10 @@ static void parse_attribute(AttributeDef *ad)
         case TOK_PACKED2:
             ad->packed = 1;
             break;
+        case TOK_WEAK1:
+        case TOK_WEAK2:
+            ad->weak = 1;
+            break;
         case TOK_UNUSED1:
         case TOK_UNUSED2:
             /* currently, no need to handle it because tcc does not
diff --git a/tcctok.h b/tcctok.h
index 9075865a..a69f6f9c 100644
--- a/tcctok.h
+++ b/tcctok.h
@@ -93,6 +93,8 @@
      DEF(TOK_ALIGNED2, "__aligned__")
      DEF(TOK_PACKED1, "packed")
      DEF(TOK_PACKED2, "__packed__")
+     DEF(TOK_WEAK1, "weak")
+     DEF(TOK_WEAK2, "__weak__")
      DEF(TOK_UNUSED1, "unused")
      DEF(TOK_UNUSED2, "__unused__")
      DEF(TOK_CDECL1, "cdecl")