bug in conditional assembly

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pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

Hello,
I updated my hwtest with the new fasm 1.71.22 and while before it compiled fine, now it gives an error at line 346 in rtl8169.asm.
This line is inside and IF 0 / END IF block, so it shouldn't give any error. If I comment it with ; there is no problem, but this looks like a bug.

Find attached my hwtest and try to run MAKEFLOP.BAT (if it compiles fine, press CTRL+C to exit).

Description:		Download
Filename:	HWTEST.7z
Filesize:	465.84 KB
Downloaded:	525 Time(s)

04 Dec 2014, 21:03

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17863
Location: In your JS exploiting you and your system

revolution

pfranz wrote:

... the new fasm 1.71.22 ...

Erm, the current version is 1.71.28.

Please try with the latest version and report again if the problem is still there.

Also, please try to post a minimal example. A 465k compressed file is not really an example to test with.

04 Dec 2014, 21:07

pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

Yes, the problem is still there also with the latest version
The example is big but I pointed out where the problem is and how to solve it, so it should be easy to deal with it. Just uncompress it and run the batch file.
I haven't tried with other situations.

04 Dec 2014, 21:21

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17863
Location: In your JS exploiting you and your system

revolution

Maybe you could just post the offending line 346 here? I'd much rather that than have to download a file, make a folder, uncompress, open a console, run a command etc.

04 Dec 2014, 21:26

pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

Here it is, it's C code (that's why is inside and IF 0 block, is kind of documentation):

cfg |= (RTL_R32(RxConfig) & rtl_chip_info[tp->chipset].RxConfigMask); ff7e1880

I don't try constructing examples as the problem could be due to the big size of the program or to something somewhere else. Only Tomasz can tell ...

04 Dec 2014, 21:31

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17863
Location: In your JS exploiting you and your system

revolution

What it appears to be is something similar to this:

Code:

if 0
x|=(&)
end if

Which gives and "invalid expression" error. Is that what you get?

04 Dec 2014, 21:39

pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

yes, "invalid expression" is the error

04 Dec 2014, 21:41

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17863
Location: In your JS exploiting you and your system

revolution

Remember that fasm has a few different stages. preprocessor/parser/assembler. Each stage is separate. The "if 0" line is processed by the assembler, but the parser is evaluating the logical consistency of the following expression before the assembler has a chance to skip assembling the line. So the error will persist because the parser has no knowledge that the line will never be assembled.

04 Dec 2014, 21:46

pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

I believe "if 0" is processed by preprocessor. Anyway, in the old versions this problem was not present

04 Dec 2014, 21:48

AsmGuru62

Joined: 28 Jan 2004
Posts: 1422
Location: Toronto, Canada

AsmGuru62

Strange, why not just comment the C code?

04 Dec 2014, 23:27

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7845
Location: Kraków, Poland

Tomasz Grysztar

Correction uploaded as 1.71.29 release.

05 Dec 2014, 12:18

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc

A fix is good, but I suppose, there's a need in a bit of clarification.

pfranz
It's still not like you are allowed to put arbitrary things into an "if 0" block.

Quote:

I believe "if 0" is processed by preprocessor.

No it's not. It's handled by the assembler. That's why the following code will still fail to compile:

Code:

macro x {}
if 0 
x|=(&) 
end if

A colon at the beginning of a line will fail to compile because of it's special handling as well:

Code:

if 0
:
end if

For unclear reasons $% is an invalid name (contrary to %$) and for the same unclear reasons the following also fails to compile:

Code:

if 0
$%
end if

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05 Dec 2014, 13:00

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7845
Location: Kraków, Poland

Tomasz Grysztar

l_inc wrote:

A fix is good, but I suppose, there's a need in a bit of clarification.

Thank you for this, I endorse everything you've written here.

l_inc wrote:

For unclear reasons $% is an invalid name (contrary to %$) ...

Names starting with "$" (and having at least one additional character) are currently always treated as numbers (the same way as ones starting with digit), hence the "invalid name" error.

05 Dec 2014, 13:17

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc

Tomasz Grysztar

Quote:

Names starting with "$" (and having at least one additional character) are currently always treated as numbers

Oh, sure. Thanks. I could have though about this.

P.S. Still I'm unable to explain it failing the compilation in an "if 0" block. It should be of no interest for the preprocessor. Is it the following parsing stage, that fails it? But aren't you aiming the parsing stage to be inseparable/indistinguishable from the assembly stage?

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Faith is a superposition of knowledge and fallacy

05 Dec 2014, 13:48

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7845
Location: Kraków, Poland

Tomasz Grysztar

l_inc wrote:

P.S. Still I'm unable to explain it failing the compilation in an "if 0" block. It should be of no interest for the preprocessor. Is it the following parsing stage, that fails it? But aren't you aiming the parsing stage to be inseparable/indistinguishable from the assembly stage?

Yes, this one could be improved, too. But it's not such an immediate fix as the above one, I would need to think about it a bit.

05 Dec 2014, 14:19

pfranz

Joined: 13 Jan 2007
Posts: 49
Location: Italy

pfranz

Thanks, now it works. I forgot that here IF is an assembler directive, I was used to other compilers where it's a preprocessor one. Maybe MATCH is the one?

05 Dec 2014, 17:52

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc

pfranz

Quote:

Maybe MATCH is the one?

match is a preprocessor directive that could allow you to skip some source code locations (except for the implications of the fix directive). But it's important to remember that the closing brace character ends the scope of macroblocks. The braces are too common for the C code, which makes macroblocks (including match) not well suitable for skipping C code processing.

The best way to comment out the C code is (surprise-surprise!) to use comments.

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06 Dec 2014, 00:47

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7845
Location: Kraków, Poland

Tomasz Grysztar

Tomasz Grysztar wrote:

l_inc wrote:
P.S. Still I'm unable to explain it failing the compilation in an "if 0" block. It should be of no interest for the preprocessor. Is it the following parsing stage, that fails it? But aren't you aiming the parsing stage to be inseparable/indistinguishable from the assembly stage?
Yes, this one could be improved, too. But it's not such an immediate fix as the above one, I would need to think about it a bit.

The bug was actually in the other place than I thought, a forgotten piece of code that was very outdated. I'm fixing it with the 1.71.30 release.

07 Dec 2014, 13:20

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