#2922 PDK compiler / assembler error when defining a label in inline assembler when used inside of a for loop

[Free-PDK]

A label defined in inline assembler (e.g. used ofr a tight busy loop) compiler / assembler will give an error if the inline aseembler block is inside of a for loop:

void main(void)
{
  for(;;)
  {
    __asm
      mov a,#7
    asmloop:  
      dzsn a
      goto asmloop
    __endasm;
  }
}

Output: build/testasmloop.asm:108: Error: undefined symbol encountered during assembly

When looking at the compiler created assembler file it looks fine (except the indentation of the label):

_main:
00102$:
; testasmloop.c: 16: __endasm;
  mov a,#7
        asmloop:
  dzsn  a
  goto  asmloop
  goto 00102$
00104$:
; testasmloop.c: 18: }
  ret

[Free-PDK]

I researched a bit more and found that the problem is caused by the assembler.

The problem is caused by mixing numeric labels ( e.g. 00102$: ) with normal labels ( e.g. label: ).

The following short assembler program shows the error:

testbad.asm:

    .area HEADER (ABS)
00102$:
label:
    goto  00102$

./sdaspdk13 test.asm
test.asm:4: Error: < u > undefined symbol encountered during assembly
removing test.rel

This version works fine:
testok.asm:

    .area HEADER (ABS)
00102$:
01234$:
    goto  00102$

[Free-PDK]

According to an old copy of SDCC user guide (e.g. from here: http://fivedots.coe.psu.ac.th/~cj/masd/resources/sdcc-doc/SDCCUdoc-13.html) it is not allowed to use normal labels in inline assembler (this matches exact the observed behaviour):

***All labels defined within inline assembler code HAS TO BE of the form nnnnn$ where nnnn is a number less than 100 (which implies a limit of utmost 100 inline assembler labels per function).

---

In contrast the current SDCC user guide (http://sdcc.sourceforge.net/doc/sdccman.pdf) does not mention this fact and also gives a BAD example (chapter 3.11):

old format:
Example

__asm
  ; This is a comment
  label:
     nop
__endasm;

new format:
Example:

__asm__ (”; This is a comment\nlabel:\n\tnop”);

[Maarten Brock]

You're right that the example is bad.

But the old explanation is still there in 3.11.4 Use of Labels within Inline Assembler

[Maarten Brock]

Please do not assign bugs to developers. It is up to the developers to pick something up and assign it to themselves.