[Nasm-bugs] [Bug 3392561] New: %ifn in a certain context allows undefined symbol, which activates its clause

[noreply-nasm at gorcunov.org]

https://bugzilla.nasm.us/show_bug.cgi?id=3392561

            Bug ID: 3392561
           Summary: %ifn in a certain context allows undefined symbol,
                    which activates its clause
           Product: NASM
           Version: 2.14.xx
          Hardware: All
                OS: All
            Status: OPEN
          Severity: normal
          Priority: Medium
         Component: Assembler
          Assignee: nobody at nasm.us
          Reporter: pushbx at 38.de
                CC: chang.seok.bae at intel.com, gorcunov at gmail.com,
                    hpa at zytor.com, nasm-bugs at nasm.us
     Obtained from: Unknown

Here's a test case in which the "Bit value is zero!" message occurs, but no
"symbol not defined before use" error happens. I assume it might be that the
preprocessor %error is somehow of a higher priority and swallows the other
error due to undefined symbol.

$ cat test.asm
        ; This macro is used to generate byte or word access to specific
        ; bits of a dword variable.
        ; %1 = token: if "~", bit value will be negated after checking
        ; %2 = instruction
        ; %3 = variable, in the form "[address]" without size specification
        ; %4 = bit value(s) to access
        ; %5 = bool: disable word access warning, defaults to 0
        ; If the value in %4 has bits set in different bytes so that
        ; a single 8- or 16-bit instruction cannot access all the bits,
        ; an error is displayed. This insures that the macro only has
        ; to generate one instruction, as a 32-bit access on 16-bit
        ; CPUs requires multiple instructions. This workaround code
        ; needs to be written specifically then, or the flags have to
        ; be re-ordered to allow the access.
%macro _opt 4-5.nolist 0
%push
%defstr %$adr %3
%strlen %$len %$adr
%substr %$tf %$adr 1
%substr %$tb %$adr %$len
%substr %$adr %$adr 2,-2
%deftok %$adr %$adr
%ifnidn %$tf,"["
 %error Invalid memory access syntax
%elifnidn %$tb,"]"
 %error Invalid memory access syntax
%elifn %4
 %error Bit value is zero! Check code.
%elifn (%4) & ~0FFh
        %2 byte [%$adr], %1(%4)
%elifn (%4) & ~0FF00h
        %2 byte [%$adr+1], %1((%4)>>8)
%elifn (%4) & ~0FF0000h
        %2 byte [%$adr+2], %1((%4)>>16)
%elifn (%4) & ~0FF000000h
        %2 byte [%$adr+3], %1((%4)>>24)
%elifn (%4) & ~0FFFFh
 %ifn %5
  %warning Macro generated word access
 %endif
        %2 word [%$adr], %1(%4)
%elifn (%4) & ~0FFFF00h
 %ifn %5
  %warning Macro generated word access
 %endif
        %2 word [%$adr+1], %1((%4)>>8)
%elifn (%4) & ~0FFFF0000h
 %ifn %5
  %warning Macro generated word access
 %endif
        %2 word [%$adr+2], %1((%4)>>16)
%else
 %error Unsupported macro usage, requires dword:
 %ifempty %1
  %error %2 dword [%$adr], %4
 %else
  %error %2 dword [%$adr], %1(%4)
 %endif
%endif
%pop
%endmacro

        ; User forms for above macro.
        ; %1 = variable, in the form "[address]" without size specification
        ; %2 = bit value(s) to access
        ; %3 = bool: disable word access warning, defaults to 0
        ; testopt tests the specified bits (using a "test" instruction) and
        ; leaves a meaningful result in ZF, as well as NC.
        ; clropt clears the specified bits (using an "and" instruction with
        ; the negated value) and leaves NC, but a random ZF.
        ; setopt sets the specified bits (using an "or" instruction) and
        ; leaves NC, NZ.
        ; xoropt toggles the specified bits (using a "xor" instruction) and
        ; leaves NC, but a random ZF.
%idefine testopt _opt ,test,
%idefine clropt _opt ~,and,
%idefine setopt _opt ,or,
%idefine xoropt _opt ,xor,


definedequ      equ 4

%if definedequ
 %warning definedequ is true
%endif

%ifdef ERROR
%if undefinedequ
 %warning undefinedequ is true
%endif
%endif

%ifdef ERROR
%if definedequ | undefinedequ
 %warning definedequ | undefinedequ is true
%endif
%endif

foo:

testopt [foo], definedequ | undefinedequ
$ nasm test.asm
test.asm:84: warning: definedequ is true [-w+user]
test.asm:101: error: (_opt:13) Bit value is zero! Check code.
$ nasm test.asm -DERROR
test.asm:88: error: symbol `undefinedequ' not defined before use
test.asm:94: error: symbol `undefinedequ' not defined before use
$ nasm -v
NASM version 2.14
$

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