Bug in processing the "-d" switch

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l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 28 Nov 2015, 17:10

It seems there was a regression in processing the "-d" switch (just checked both the windows and linux version):

Code:

fasm -dx=0 test.asm
flat assembler  version 1.71.48  (16384 kilobytes memory)
error: source file not found.

It works OK though if the "-d" switch is at the end of the command line.

I also had this situation once, but it's not stably reproducible:

Code:

P.S. Sorry, posted to the wrong forum. Please, move it to compiler internals.

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28 Nov 2015, 17:10

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8394
Location: Kraków, Poland

Tomasz Grysztar 05 Dec 2015, 13:21

I think neither of them is consistently reproducible, or I need more details about the environment, because I was not able to get the "source file not found" error as shown in your post.

05 Dec 2015, 13:21

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 05 Dec 2015, 23:12

Tomasz Grysztar
I couldn't reproduce the bug in Windows today, but luckily it was still manifesting in Linux. The problem is how you handle the stack:

Code:

        mov     [command_line],esp
        pop     eax
        lea     esp,[esp+eax*4]
        pop     eax
        pop     [environment]
        call    get_params

This is what happens at the beginning. argc and argv are beyond the stack limits, but are still on the stack and are gonna be used. Keeping data above (at addresses lower than) the current stack pointer is careless by itself, but then you do multiple calls and overwrite pointers to the command line arguments in your own code. In my examples call convert_definition_option is the instruction that overwrites the pointer to the source file name with the return pointer.

P.S. I made a little trace with gdb, if you'd like to look in there. There's a state of registers in the order eax, ebx, ecx, edx, esi, edi, ebp, esp after each instruction executed.

Description:		Download
Filename:	trace.7z
Filesize:	29.76 KB
Downloaded:	788 Time(s)

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05 Dec 2015, 23:12

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 03 Jan 2016, 01:12

Tomasz Grysztar
I noticed that you'd fixed the bug, but now you get the environment incorrectly. It should be mov ebx,[esp+4+ecx*4+4] instead of lea ebx,[esp+4+4+ecx*4+4] .

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03 Jan 2016, 01:12

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