weak function symbols

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();
+    }
+}

examples/weak_f.c

@@ -0,0 +1,6 @@
+#include <tcclib.h>
+
+void weak_f (void)
+{
+    printf("Weak\n");
+}

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);

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))
 

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

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")