Re: as/ld silently creates programs with undefined references/symbols

[Nick Clifton]

Hi Russell,

> ld version:
>
>   GNU ld version 2.14 20030612

Just to note, version 2.15 is now out, although this version also has 
this bug.

>   arm-linux-as -o t.o t.s
>   arm-linux-ld -o t t.o --no-undefined
>
> Object/Source file (t.s) content:
>
>         .globl  _start
> _start:
>         add     r0, r0, #UNDEFINED_SYMBOL
>         mov     pc, lr
>
> Observed behaviour:
>
>   arm-linux-as silently builds the object file.

This is the bug.  There is no reloc to fixup the add instruction so the 
assembler should never have accepted the unresolved symbol.  Please 
could you try the attached patch (made against the 2.14 sources) and let 
me know how it behaves for you.  If it works I will update the mainline 
sources and you can publish the patch on the ARM Linux web site.

Cheers
  Nick

gas/ChangeLog
2004-07-01  Nick Clifton  <address@hidden>

        * config/tc-arm.c (md_apply_fix3:BFD_RELOC_ARM_IMMEDIATE): Do not
        allow values which have come from undefined symbols.
        Always consider this fixup to have been processed as a reloc
        cannot be generated for it.


Index: gas/config/tc-arm.c
===================================================================
RCS file: /work/repositories/sourceware/src/gas/config/tc-arm.c,v
retrieving revision 1.140.2.1
diff -c -3 -p -r1.140.2.1 tc-arm.c
*** gas/config/tc-arm.c 13 Jun 2003 16:34:31 -0000      1.140.2.1
--- gas/config/tc-arm.c 1 Jul 2004 17:22:43 -0000
*************** md_apply_fix3 (fixP, valP, seg)
*** 10693,10698 ****
--- 10693,10712 ----
    switch (fixP->fx_r_type)
      {
      case BFD_RELOC_ARM_IMMEDIATE:
+       /* We claim that this fixup has been processed here,
+        even if in fact we generate an error because we do
+        not have a reloc for it, so tc_gen_reloc will reject it.  */
+       fixP->fx_done = 1;
+ 
+       if (fixP->fx_addsy
+         && ! S_IS_DEFINED (fixP->fx_addsy))
+       {
+         as_bad_where (fixP->fx_file, fixP->fx_line,
+                       _("undefined symbol %s used as an immediate value"),
+                       S_GET_NAME (fixP->fx_addsy));
+         break;
+       }
+ 
        newimm = validate_immediate (value);
        temp = md_chars_to_number (buf, INSN_SIZE);
  
*************** md_apply_fix3 (fixP, valP, seg)
*** 10709,10715 ****
  
        newimm |= (temp & 0xfffff000);
        md_number_to_chars (buf, (valueT) newimm, INSN_SIZE);
-       fixP->fx_done = 1;
        break;
  
      case BFD_RELOC_ARM_ADRL_IMMEDIATE:
--- 10723,10728 ----