Use RELA relocations properly for R_DATA_PTR on x86_64.

libtcc.c: Add greloca, a generalisation of greloc that takes an addend.
tcc.h: Add greloca and put_elf_reloca.
tccelf.c: Add put_elf_reloca, a generalisation of put_elf_reloc.
tccgen.c: On x86_64, use greloca instead of greloc in init_putv.

libtcc.c

@@ -536,7 +536,8 @@ ST_FUNC void put_extern_sym(Sym *sym, Section *section,
 }
 
 /* add a new relocation entry to symbol 'sym' in section 's' */
-ST_FUNC void greloc(Section *s, Sym *sym, unsigned long offset, int type)
+ST_FUNC void greloca(Section *s, Sym *sym, unsigned long offset, int type,
+                     unsigned long addend)
 {
     int c = 0;
     if (sym) {
@@ -545,7 +546,12 @@ ST_FUNC void greloc(Section *s, Sym *sym, unsigned long offset, int type)
         c = sym->c;
     }
     /* now we can add ELF relocation info */
-    put_elf_reloc(symtab_section, s, offset, type, c);
+    put_elf_reloca(symtab_section, s, offset, type, c, addend);
+}
+
+ST_FUNC void greloc(Section *s, Sym *sym, unsigned long offset, int type)
+{
+    greloca(s, sym, offset, type, 0);
 }
 
 /********************************************************/

tcc.h

@@ -1074,6 +1074,7 @@ ST_FUNC Section *find_section(TCCState *s1, const char *name);
 ST_FUNC void put_extern_sym2(Sym *sym, Section *section, addr_t value, unsigned long size, int can_add_underscore);
 ST_FUNC void put_extern_sym(Sym *sym, Section *section, addr_t value, unsigned long size);
 ST_FUNC void greloc(Section *s, Sym *sym, unsigned long offset, int type);
+ST_FUNC void greloca(Section *s, Sym *sym, unsigned long offset, int type, unsigned long addend);
 
 ST_INLN void sym_free(Sym *sym);
 ST_FUNC Sym *sym_push2(Sym **ps, int v, int t, long c);
@@ -1261,6 +1262,7 @@ ST_FUNC int put_elf_sym(Section *s, addr_t value, unsigned long size, int info,
 ST_FUNC int add_elf_sym(Section *s, addr_t value, unsigned long size, int info, int other, int sh_num, const char *name);
 ST_FUNC int find_elf_sym(Section *s, const char *name);
 ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset, int type, int symbol);
+ST_FUNC void put_elf_reloca(Section *symtab, Section *s, unsigned long offset, int type, int symbol, unsigned long addend);
 
 ST_FUNC void put_stabs(const char *str, int type, int other, int desc, unsigned long value);
 ST_FUNC void put_stabs_r(const char *str, int type, int other, int desc, unsigned long value, Section *sec, int sym_index);

tccelf.c

@@ -269,8 +269,8 @@ ST_FUNC int add_elf_sym(Section *s, addr_t value, unsigned long size,
 }
 
 /* put relocation */
-ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
+ST_FUNC void put_elf_reloca(Section *symtab, Section *s, unsigned long offset,
-                          int type, int symbol)
+                            int type, int symbol, unsigned long addend)
 {
     char buf[256];
     Section *sr;
@@ -292,10 +292,19 @@ ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
     rel->r_offset = offset;
     rel->r_info = ELFW(R_INFO)(symbol, type);
 #ifdef TCC_TARGET_X86_64
-    rel->r_addend = 0;
+    rel->r_addend = addend;
+#else
+    if (addend)
+        tcc_error("non-zero addend on REL architecture");
 #endif
 }
 
+ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
+                           int type, int symbol)
+{
+    put_elf_reloca(symtab, s, offset, type, symbol, 0);
+}
+
 /* put stab debug information */
 
 ST_FUNC void put_stabs(const char *str, int type, int other, int desc,

tccgen.c

@@ -5201,19 +5201,35 @@ static void init_putv(CType *type, Section *sec, unsigned long c,
         case VT_LLONG:
             *(long long *)ptr |= (vtop->c.ll & bit_mask) << bit_pos;
             break;
-        case VT_PTR:
+        case VT_PTR: {
-            if (vtop->r & VT_SYM) {
+            addr_t val = (vtop->c.ptr_offset & bit_mask) << bit_pos;
+#ifdef TCC_TARGET_X86_64
+            if (vtop->r & VT_SYM)
+                greloca(sec, vtop->sym, c, R_DATA_PTR, val);
+            else
+                *(addr_t *)ptr |= val;
+#else
+            if (vtop->r & VT_SYM)
                 greloc(sec, vtop->sym, c, R_DATA_PTR);
-            }
+            *(addr_t *)ptr |= val;
-            *(addr_t *)ptr |= (vtop->c.ptr_offset & bit_mask) << bit_pos;
+#endif
             break;
-        default:
+        }
-            if (vtop->r & VT_SYM) {
+        default: {
+            int val = (vtop->c.i & bit_mask) << bit_pos;
+#ifdef TCC_TARGET_X86_64
+            if (vtop->r & VT_SYM)
+                greloca(sec, vtop->sym, c, R_DATA_PTR, val);
+            else
+                *(int *)ptr |= val;
+#else
+            if (vtop->r & VT_SYM)
                 greloc(sec, vtop->sym, c, R_DATA_PTR);
-            }
+            *(int *)ptr |= val;
-            *(int *)ptr |= (vtop->c.i & bit_mask) << bit_pos;
+#endif
             break;
         }
+        }
         vtop--;
     } else {
         vset(&dtype, VT_LOCAL|VT_LVAL, c);