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> Compiler Internals > Having problems with "section '.bss' readable writeable |
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LocoDelAssembly
Maybe you defined some data instead of reserving space?
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04 Nov 2006, 16:48 |
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Tomasz Grysztar
That's the most probable reason. The name of the section doesn't matter - as long as you put only the data reservation directives in it (or, at least, at the end of it), that space is not allocated within the output file.
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04 Nov 2006, 17:09 |
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madmatt
I've done it the same as I have done it before without problems until now. Another thought, it may be working right and I'm reserving too much data? What is the data limit for the '.bss" section? Below is what I'm trying to reserve.
Code: d3d9Textures IDirect3DTexture9 ;pointers to texture objects dd MAXTEXTURES dup(?) ;MAXTEXTURES = 2048 d3d9Surfaces IDirect3DSurface9 ;pointers to surface objects dd MAXD3DSURFACES dup(?) ;MAXD3DSURFACES = 256 d3d9primitive CustomVertex db 2048 * (sizeof.CustomVertex * 5) dup(?) ; sizeof.CustomVertex = 20 d3d9texture CustomVertexUV db 2048 * (sizeof.CustomVertexUV * 5) dup(?) ;sizeof.CustomVertexUV = 28 ddsurfaces SURFACES db sizeof.SURFACES * MAXSURFACES dup(?) ; DDMAXSURFACES = 2048 soundfx pcmsoundtype db MAXSOUNDS*sizeof.pcmsoundtype dup(?) ;MAXSOUNDS = 2048 chfilename db MAX_PATH dup(?) debugtxt db 256 dup(?) palette PALETTEENTRY ;main palette db sizeof.PALETTEENTRY*255 dup(?) workpal PALETTEENTRY ;working palette for color rotations db sizeof.PALETTEENTRY*255 dup(?) scanlinetable dd 2050 dup(?) ;can draw up to a screen size of 2048 scanlines dscanlinetable dd 2050 dup(?) temp768 db 768 dup(?) ftoaenv: times 28 db ? |
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04 Nov 2006, 19:23 |
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Tomasz Grysztar
Check out whether any of your structures (like IDIrect3DTexture9 etc.) doesn't contain any initialized data. As I said, that is the only possible reason I'm aware of that may cause the section data to be put into file.
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05 Nov 2006, 01:24 |
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madmatt
I've narrowed the problem to the two definitions below:
Code: d3d9primitive CustomVertex
db 2048 * (sizeof.CustomVertex * 5) dup(?)
d3d9texture CustomVertexUV
db 2048 * (sizeof.CustomVertexUV * 5) dup(?)
I've checked the two structures above and they WERE defining data, I did fix them, but that did not solve the problem. 
Maybe there is a 64KB (65535 bytes) limit on the data that can be reserved? If so, I'll just go ahead and use manual allocation of memory. |
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05 Nov 2006, 10:07 |
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Tomasz Grysztar
There are not limits of any kind or anything like that. Please post some complete code, from your small samples the reason remains invisible.
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05 Nov 2006, 12:30 |
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madmatt
Here is how I have it set up, before and after the .bss section:
Code: section '.data' data readable writeable include 'Utilities\Utilities_VARIABLES.inc' include 'DirectDraw\DirectDraw_VARIABLES.inc' include 'DirectVideo\DirectVideo_VARIABLES.inc' include 'D2D9\D2D9_VARIABLES.INC' include 'DirectInput\DirectInput_VARIABLES.inc' include 'DirectSound\DirectSound_VARIABLES.inc' section '.bss' readable writeable d3d9Textures IDirect3DTexture9 ;pointers to texture objects dd MAXTEXTURES dup(?) d3d9Surfaces IDirect3DSurface9 ;pointers to surface objects dd MAXD3DSURFACES dup(?) d3d9primitive CustomVertex db 2048 * (sizeof.CustomVertex * 5) dup(?) d3d9texture CustomVertexUV db 2048 * (sizeof.CustomVertexUV * 5) dup(?) ddsurfaces SURFACES db sizeof.SURFACES * MAXSURFACES dup(?) soundfx pcmsoundtype db MAXSOUNDS*sizeof.pcmsoundtype dup(?) chfilename db MAX_PATH dup(?) debugtxt db 256 dup(?) palette PALETTEENTRY ;main palette db sizeof.PALETTEENTRY*255 dup(?) workpal PALETTEENTRY ;working palette for color rotations db sizeof.PALETTEENTRY*255 dup(?) scanlinetable dd 2050 dup(?) ;can draw up to a screen size of 2048 scanlines dscanlinetable dd 2050 dup(?) temp768 db 768 dup(?) ftoaenv: times 28 db ? ; *** A L L C O D E L I B R A R Y C O M P O N E N T S ** section '.code' code readable executable proc DllOk hinst, Reason, Reserved .if [Reason] = DLL_PROCESS_ATTACH call CpuProcessorInfo call RndMakeSeed return TRUE .elseif [Reason] = DLL_PROCESS_DETACH ;shutdown stuff here return TRUE .endif return FALSE endp and the structures: Code: MAXTEXTURES equ 2048 MAXD3DSURFACES equ 256 struct CustomVertex ;non-textured drawing x dd ? y dd ? z dd ? rhw dd ? diffuse dd ? ends struct CustomVertexUV ;textured (sprite) drawing x dd ? y dd ? z dd ? rhw dd ? diffuse dd ? u dd ? v dd ? ends Again, I comment the two defines below, and everything compiles to 100kb, I uncomment the two defines below, and the code becomes 500kb: Code: d3d9primitive CustomVertex
db 2048 * (sizeof.CustomVertex * 5) dup(?)
d3d9texture CustomVertexUV
db 2048 * (sizeof.CustomVertexUV * 5) dup(?)
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05 Nov 2006, 16:46 |
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Tomasz Grysztar
Can you provide also the definitions of structures like IDirect3DTexture9 etc. that you use? They're not in the standard set of includes.
The best would be if you provided the whole set of headers that you use. |
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05 Nov 2006, 16:49 |
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madmatt
 You guys were right after all, I checked my OTHER structures and they were defining data, so I fixed them and everything is working good again,  Even us old dog programmers make stupid mistakes from time to time!  and then broadcast it on a great forum like this  |
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05 Nov 2006, 17:01 |
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rhyde
Tomasz Grysztar wrote: That's the most probable reason. The name of the section doesn't matter - as long as you put only the data reservation directives in it (or, at least, at the end of it), that space is not allocated within the output file. I've been having some linker issues lately (MSLINK and POLINK) that are related to this problem. In particular, FASM, in some cases, seems to be setting *both* the "initialized data" and "uninitialized data" COFF flags. This generates warnings by the linker when combined with sections that don't have both flags set (and it seems unusual to have both flags set in a section). I'd also recommend adding a new section type, bss (like 'code' and 'data') that would cause the assembler to generate a warning or error message if the program contains any data-defining directives in the section. This would help avoid questions like this thread's parent. Cheers, Randy Hyde |
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03 May 2007, 17:11 |
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rhyde
rhyde wrote:
I guess I forgot the justification for such a change. I've run into a problem when I have a section generated that has zero length (because it's program generated, largely to pass along segment ordering to the linker). FASM sees no data in the section and automatically attaches a "Uninitialized Data" flag to the guy. If I've put the 'data' flag on it, I wind up with a COFF flags value of something like XXXXXX80. When a second section declaration comes along that *does* have data associated with it, the two get OR'd together producing XXXXXXC0. When I link this against library code, that typically has an XXXXXX80 or XXXXXX40 flag value, the linker issues a warning. It would be *really* nice to be able to say "data sections have the flag XXXXXX40" and "bss sections have the flag XXXXXX80" and leave it at that. The size of the sections shouldn't come into play (other than, perhaps, as some default if nothing else is specified). What I'd really like is to be able to do something like this for COFF: section 'data' data readable writeable align 16 -and- section 'bss' bss readable writeable align 16 When (if) FASM combines sections in the same source file, it should do something reasonable, specifically, the combination of an initialized data section and an uninitialized data section should produce an initialized data section (including bloating out the section). It would be cool to issue a warning in case this happens. As I pointed out in the last post, if you support the bss (uninitialized data) section flag, you should probably emit an error message if they use a data generating declaration. Adding the BSS flag is really easy. I did that in a few minutes when playing around with the FASM source code (i.e., add the line <<db 3,"bss",19h,7>> to the formatter_symbols table). The code following the "section_flag" label needs to be tweaked to avoid OR'ing the bss and data flags together into the same value (though I'm not absolutely positive this is the only place this work needs to be done). The real trick is modifying the code that handles the data declaration directives so that it emits a warning if someone tries to declare data in a bss section. Cheers, Randy Hyde |
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03 May 2007, 17:33 |
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asmfan
Wow Randall Hyde is here) Nice to meet you here.
I agree that needed /but not special necessary for good programmer  / some keyword to mark section as physical empty (but not virtual) to avoid some init data in it, although uninit data can be stored as last part of init data (as ms linker does - .data? is joined to .data).
also DATA directive after SECTION means initialized data flag, while lack of it means uninitialized. |
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03 May 2007, 17:34 |
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rhyde
asmfan wrote: Wow Randall Hyde is here) Nice to meet you here. The only problem with the "not necessary for good programmer" policy is that "not necessarily good programmers" often use the product. Quote:
Alas, the lack of it does *not* set the uninitialized data flag ($80). This is, perhaps, a defect in the design of COFF, I haven't looked into why you would want to have both flags set (maybe specifiying that the last part of the section is uninitialized data?). In any case, I'm trying to eliminate linker warnings which are easy enough for advanced programmers to filter out, but freak out beginners. Of course, I wonder what the linker winds up doing when it has two sections that have both flags set. That would be an interesting situation to try and resolve. I personally feel more comfortable keeping initialized and uninitialized data in separate sections; sure, the linker might concatenate the sections when forming the final executable, but for OBJ files, I'd want them kept separate. Cheers, Randy Hyde |
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03 May 2007, 19:07 |
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vid
BSS section is NOT uninitialized. It is zeroed (due to any definition i can find).
BTW, That's why you have to use this Code: int MyVar=1; Code: int MyVar=0; So "bss" is not probably not really same as "uninitialized"... |
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03 May 2007, 19:22 |
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rhyde
vid wrote: BSS section is NOT uninitialized. It is zeroed (due to any definition i can find). This is true. However, the "uninitialized data" flag in the COFF section header is simply telling us that the data (which is all zeros) is not physically present in the object code file, it is the loader's responsibility to zero out memory when it loads the program into memory. Quote:
Traditionally, BSS is the section name given to the "uninitialized" section. It wasn't always zeroed, but when timesharing OSes came around in the 1960s and security became a concern, the "uninitialized sections" were zeroed out when the program was loaded into memory. Languages like C came to rely upon this implicit initialization. In any case, the sections I'm talking about *are* zeroed. They are called "uinitialized" because the programmer doesn't specifically provide an initial value for each value in that block -- the assumption is either that whatever initial value it has is irrelevant, or that (in modern OSes) it is automatically initialized with zeros when loaded into memory. The difference between the "initialized data" and "uninitialized data" flags in the COFF format is file size. Because initialized data section might contain values other than zero, each and every byte of an initialized data section has to be present in the executable file. For uninitialized data sections, there is no need to take up one byte of space for each variable byte in the program; instead, all you need is the size of the section and the OS can automatically reserve that storage (and, as it turns out, zero out that storage). This makes EXEs a whole lot smaller if you've got a lot of static, uninitialized, data. The problem I'm reporting is that the COFF section header is rather stupid. It has one bit for initialized data sections and a separate bit for uninitialized sections. Therefore, it is physically possible to set both bits (and, in certain circumstances, it appears that FASM does exactly this). However, having both bits set doesn't make sense (at least, not to me). You can't have *both* attributes for the same block of data, it's either initialized or not. Now the COFF section header *does* provide two fields: SizeOfInitializedData and SizeOfUninitializedData, so I assume that it *might* be possible to have initialized data at the beginning of a section and specify a block of uninitialized data at the end of the section, but as I mentioned in a previous post, it's a bit difficult to merge two such sections (containing both initialized and uninitialized data). In any case, I'm winding up with some cases where FASM winds up setting both of these flag bits (and other times does not) and the Microsoft linker likes to complain at that point. My preferred solution is to be able to explicitly state that a given section contains initialized data or not. Cheers, Randy Hyde |
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03 May 2007, 20:49 |
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