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Re: [Tinycc-devel] Fix gcall_or_jmp to VT_CONST symbol in arm-gen.c


From: Christian Jullien
Subject: Re: [Tinycc-devel] Fix gcall_or_jmp to VT_CONST symbol in arm-gen.c
Date: Sat, 22 Dec 2018 19:17:23 +0100

I tested your patch on ARM board (RPi) and it works. I reintroduced zfunc
test for this system in 07_function.c

Thanks

-----Original Message-----
From: Tinycc-devel [mailto:address@hidden
On Behalf Of Pursuer
Sent: samedi 22 d├ęcembre 2018 14:05
To: tinycc-devel
Subject: [Tinycc-devel] Fix gcall_or_jmp to VT_CONST symbol in arm-gen.c

I try to compile code like below with tcc:
void zfunc()
{
        ((void (*)(void))0) ();
}
and tcc broken with SegmengFault.

tcc was buit to target armv7l and run on Windows host.

I found that the implemention of gcall_or_jmp in arm_gen.c caused that.  I
try to fix this problem.  It seem worked. Though I only tested on Windows
and checked the generated file with arm-objdump.

$ git diff arm-gen.c
diff --git a/arm-gen.c b/arm-gen.c
index 634cffb..c5de065 100644
--- a/arm-gen.c
+++ b/arm-gen.c
@@ -739,25 +739,28 @@ static void gadd_sp(int val)
 static void gcall_or_jmp(int is_jmp)
 {
   int r;
+  uint32_t x;
   if ((vtop->r & (VT_VALMASK | VT_LVAL)) == VT_CONST) {
-    uint32_t x;
     /* constant case */
-    x=encbranch(ind,ind+vtop->c.i,0);
-    if(x) {
-      if (vtop->r & VT_SYM) {
-       /* relocation case */
-       greloc(cur_text_section, vtop->sym, ind, R_ARM_PC24);
-      } else
-       put_elf_reloc(symtab_section, cur_text_section, ind, R_ARM_PC24, 0);
-      o(x|(is_jmp?0xE0000000:0xE1000000));
-    } else {
-      if(!is_jmp)
-       o(0xE28FE004); // add lr,pc,#4
-      o(0xE51FF004);   // ldr pc,[pc,#-4]
-      if (vtop->r & VT_SYM)
-       greloc(cur_text_section, vtop->sym, ind, R_ARM_ABS32);
-      o(vtop->c.i);
-    }
+       if(vtop->r & VT_SYM){
+               x=encbranch(ind,ind+vtop->c.i,0);
+               if(x) {
+               /* relocation case */
+                 greloc(cur_text_section, vtop->sym, ind, R_ARM_PC24);
+                 o(x|(is_jmp?0xE0000000:0xE1000000));
+               } else {
+                       if(!is_jmp)
+                               o(0xE28FE004); // add lr,pc,#4
+                       o(0xE51FF004);   // ldr pc,[pc,#-4]
+                       greloc(cur_text_section, vtop->sym, ind,
R_ARM_ABS32);
+                       o(vtop->c.i);
+               }
+       }else{
+               if(!is_jmp)
+                       o(0xE28FE004); // add lr,pc,#4
+               o(0xE51FF004);   // ldr pc,[pc,#-4]
+               o(vtop->c.i);
+       }
   } else {
     /* otherwise, indirect call */
     r = gv(RC_INT);
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