From e03306d1709d13d2e67349d42488a93abc4dc32a Mon Sep 17 00:00:00 2001
From: grischka <grischka>
Date: Sat, 1 Oct 2016 21:58:23 +0200
Subject: [PATCH] tccelf: allow multiple declaration of bss/common symbols

also in combination with one initialized:

For example
  1.c
     int xxx;
  2.c
     int xxx = 2;
  3.c
     int xxx;

tcc 1.c 2.c 3.c
---
 tccelf.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tccelf.c b/tccelf.c
index 0aa70144..23c7e9b7 100644
--- a/tccelf.c
+++ b/tccelf.c
@@ -236,11 +236,14 @@ ST_FUNC int add_elf_sym(Section *s, addr_t value, unsigned long size,
                 /* keep first-found weak definition, ignore subsequents */
             } else if (sym_vis == STV_HIDDEN || sym_vis == STV_INTERNAL) {
                 /* ignore hidden symbols after */
-            } else if (esym->st_shndx == SHN_COMMON
-                    && (sh_num < SHN_LORESERVE || sh_num == SHN_COMMON)) {
-                /* gr: Happens with 'tcc ... -static tcctest.c' on e.g. Ubuntu 6.01
-                   No idea if this is the correct solution ... */
+            } else if ((esym->st_shndx == SHN_COMMON
+                            || esym->st_shndx == bss_section->sh_num)
+                        && (sh_num < SHN_LORESERVE
+                            && sh_num != bss_section->sh_num)) {
+                /* data symbol gets precedence over common/bss */
                 goto do_patch;
+            } else if (sh_num == SHN_COMMON || sh_num == bss_section->sh_num) {
+                /* data symbol keeps precedence over common/bss */
             } else if (s == tcc_state->dynsymtab_section) {
                 /* we accept that two DLL define the same symbol */
             } else {
@@ -248,7 +251,7 @@ ST_FUNC int add_elf_sym(Section *s, addr_t value, unsigned long size,
                 printf("new_bind=%x new_shndx=%x new_vis=%x old_bind=%x old_shndx=%x old_vis=%x\n",
                        sym_bind, sh_num, new_vis, esym_bind, esym->st_shndx, esym_vis);
 #endif
-                tcc_error_noabort("'%s' defined twice... may be -fcommon is needed?", name);
+                tcc_error_noabort("'%s' defined twice", name);
             }
         } else {
         do_patch: