Linux X demo
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From: T.M. Sommers on 27 Jul 2007 08:03 Rod Pemberton wrote: > > Snipping the historical 1-7 as both you an T.M. Sommers did, also distorts > my entire post... To which, it appears that five or six others who never > read it responded... I snipped it because it was irrelevant. It does not matter what K&R said, or what PCC did. C is defined today by the standard. -- Thomas M. Sommers -- tms(a)nj.net -- AB2SB
From: Frank Kotler on 28 Jul 2007 10:59 Herbert Kleebauer wrote: > Frank Kotler wrote: > > >>I haven't figured out why the "direct to binary" version isn't working. > > > Here a working version. Thank you Herbert!!! Sorry for the delayed reply. Like the careless butcher, I've gotten a little behind in my work... > It's ugly, Yes. > but either NASM is missing some > important features or I don't understand how to proper use NASM. Possibly both? > The nop's are in again so I could do a binary compare with the > original binary. Okay. > ; nasm -O999 -f bin -o myprog myprog.asm I found that "-O999" caught a couple of "optimization opportunities" that you missed. Are you getting a good "binary compare"? "My version" (not working - "broken pipe" - I *hate* it when that happens!) is a few bytes smaller than the Lindela version, identical in size to your Nasm version. > %macro dc.b 2+ Wow! You went to the trouble to learn Nasm's macro systen!!! This is similar in principle tho how Brian's "elf.inc" does it. I'm *trying* to avoid that... .... > ; don't remove the following line and use offs directly > ; this seems to be a bug in NASM > offs2 equ offs > ;=========================================================================== I don't know what's going on here. Haven't experimented. I shall. > @1 equ $08048000 ; virtual address of code start > @@1 equ 0 ; file byte address of code start Okay, using symbols like "@1", "@@1", "@2", "@@2", "@3" is not Nasm's fault. People have different ideas of "beauty" and "beastliness", I guess. *I* don't feel that this helps. .... > ; you MUST NOT use db/dw/dd to define data, use dc.b/dc.w/dc.l instead I *think* Nasm's got the ability to avoid this... I just can't get it to *work*! When you're digging yourself deeper and deeper into a whole, quit digging. When you get lost, go back to something simple, and work up to it again. In hopes that this may work, here's a simple test of Nasm's supposed abilities. You want to be able to alter "org" or "$"... Nasm doesn't do it that way. Mike Ter Louw's "multisection support" for "-f bin" gives us "start", "vstart", "align", "valign", "follows", "vfollows", etc. This should give us complete control over the placement and alignment of sections, and allow us to separate the "virtual address" from the physical file position. [map all sectest.map] bits 32 org 8048000h section .text dd FOO dd BAR dd BAZ mov eax, foodat mov eax, bardat mov eax, bazdat mov eax, z_end foodat dd 42 FOO equ $ - $$ section .data valign=4096 bardat dd 43 misalign db 0 BAR equ $ - $$ section .bss vfollows=.data valign=1 bazdat resd 41 z_end resb 1 BAZ equ $ - $$ Here's the map file: - NASM Map file --------------------------------------------------------------- Source file: sectest.asm Output file: sectest.bin -- Program origin ------------------------------------------------------------- 08048000 -- Sections (summary) --------------------------------------------------------- Vstart Start Stop Length Class Name 08048000 08048000 08048024 00000024 progbits .text 08049000 08048024 08048029 00000005 progbits .data 08049005 08049005 080490AA 000000A5 nobits .bss -- Sections (detailed) -------------------------------------------------------- ---- Section .text ------------------------------------------------------------ class: progbits length: 00000024 start: 08048000 align: not defined follows: not defined vstart: 08048000 valign: not defined vfollows: not defined ---- Section .data ------------------------------------------------------------ class: progbits length: 00000005 start: 08048024 align: 00000004 follows: not defined vstart: 08049000 valign: 00001000 vfollows: not defined ---- Section .bss ------------------------------------------------------------- class: nobits length: 000000A5 start: 08049005 align: not defined follows: not defined vstart: 08049005 valign: 00000001 vfollows: .data -- Symbols -------------------------------------------------------------------- ---- No Section --------------------------------------------------------------- Value Name 00000024 FOO 00000005 BAR 000000A5 BAZ 00000024 FOO 00000005 BAR 000000A5 BAZ (dunno why these are duplicated....) ---- Section .text ------------------------------------------------------------ Real Virtual Name 08048020 08048020 foodat ---- Section .data ------------------------------------------------------------ Real Virtual Name 08048024 08049000 bardat 08048028 08049004 misalign ---- Section .bss ------------------------------------------------------------- Real Virtual Name 08049005 08049005 bazdat 080490A9 080490A9 z_end And here's the disassembly: 08048000 2400 and al,0x0 08048002 0000 add [eax],al 08048004 05000000A5 add eax,0xa5000000 08048009 0000 add [eax],al 0804800B 00 db 0x00 0804800C B820800408 mov eax,0x8048020 08048011 B800900408 mov eax,0x8049000 08048016 B805900408 mov eax,0x8049005 0804801B B8A9900408 mov eax,0x80490a9 08048020 2A00 sub al,[eax] 08048022 0000 add [eax],al 08048024 2B00 sub eax,[eax] 08048026 0000 add [eax],al 08048028 00 db 0x00 Does this look like what I'm trying to do? I think it's doing what I intend, but when I expand the same technique to the "full version", I'm getting something subtly(?) wrong. Lemme go back to banging on it (I really haven't spent much time with it since the initial "translation" - lotsa distractions). (~h)Later, Frank
From: Herbert Kleebauer on 28 Jul 2007 14:48 Frank Kotler wrote: > Herbert Kleebauer wrote: > > ; nasm -O999 -f bin -o myprog myprog.asm > > I found that "-O999" caught a couple of "optimization opportunities" > that you missed. Wouldn't say "missed", better "don't care". I always start with short branches and change them to long branches if I get an error. But if I rearrange the code I never check if I can convert a long branch back to a short branch. And also for cmp/add/sub I often forget that there is a short form. > Are you getting a good "binary compare"? After converting unnecessary long to short branches and using the short form of add/sub/cmp I got identical binaries. This was surprising because normally my encoding of reg,reg is the opposite way as other assemblers do. > > %macro dc.b 2+ > > Wow! You went to the trouble to learn Nasm's macro systen!!! This is > similar in principle tho how Brian's "elf.inc" does it. I'm *trying* to > avoid that... Didn't see any other way. But maybe I should have read the NASM manual. > > > @1 equ $08048000 ; virtual address of code start > > @@1 equ 0 ; file byte address of code start > > Okay, using symbols like "@1", "@@1", "@2", "@@2", "@3" is not Nasm's > fault. People have different ideas of "beauty" and "beastliness", I > guess. *I* don't feel that this helps. In Lindela @ is the symbol for the current location counter ($ in NASM) and @@ is the symbol for the output file position counter. And because NASM doesn't allow a redefine of a symbol I had to add a number (@1, @2,..) > I *think* Nasm's got the ability to avoid this... I just can't get it to > *work*! I got it to work now. But I must say it still was more try and error than really understanding the logic behind NASM (must be something the same way as the Intel syntax logic). > bin" gives us "start", "vstart", "align", "valign", "follows", > "vfollows", etc. This should give us complete control over the placement > and alignment of sections, and allow us to separate the "virtual > address" from the physical file position. Maybe the documentation could be a little bit more clear. Anyhow, here a working version: ;=========================================================================== ; A simple graphics demo for Linux/X by Frank Kotler & ASCII Annie ; nasm -O999 -f bin -o myprog myprog.asm ;=========================================================================== orig equ $08048000 code_addr equ orig code_offset equ 0 section .text vstart=code_addr ;=========================================================================== ;--------------------------- ELF header ----------------------------------- dd $464c457f,$00010101,0,0,$00030002,1,main,$34,0,0,$00200034,2,0 dd 1,code_offset,code_addr,code_addr,code_filez,code_memsz,5,4096 dd 1,data_offset,data_addr,data_addr,data_filez,data_memsz,6,4096 ;--------------------------- code ------------------------------------------ USE32 main: mov [stack_ptr], esp ; save initial stack pointer ; ******************** get socket handle *************************** push 0 ; no protocol specified push 1 ; 1: SOCK_STREAM (/usr/include/linux/net.h) push 1 ; 1: AF_UNIX, AF_LOCAL (/usr/include/linux/socket.h) mov ecx, esp ; pointer to parameter for "socket" mov ebx, 1 ; "socket" (/usr/include/linux/net.h) mov eax, 102 ; socketcall (/usr/include/asm/unistd.h) int 80h add esp, 3 * 4 ; free space for parameters test eax, eax ; ERROR js err ; my apologies for propagating this sloppiness. ; really should be "cmp eax, -4096" (or -4095?) ; won't happen here, but we *could* get a ; valid return over 2G! - fbk mov [x_handle], eax ; ********** connect socket to /tmp/.X11-unix/X0" ****************** push sockaddr_un_l push sockaddr_un ; (/usr/include/linux/un.h) push dword [x_handle] ; socket handle mov ecx, esp ; pointer to parameter for "connect" mov ebx, 3 ; "connect" (/usr/include/linux/net.h) mov eax, 102 ; socketcall (/usr/include/asm/unistd.h) int 80h add esp, 3 * 4 ; free space for parameters test eax, eax ; ERROR js err ; *************** make socket read non blocking ******************* mov ebx, [x_handle] ; socket handle mov ecx, 3 ; F_GETFL (/usr/include/asm/fcntl.h) mov eax, 55 ; fcntl (/usr/include/asm/unistd.h) int 80h test eax, eax ; ERROR js err mov ebx, [x_handle] ; socket handle mov ecx, 4 ; F_SETFL (/usr/include/asm/fcntl.h) mov edx, eax or edx, 800h ; O_NONBLOCK (/usr/include/asm/fcntl.h) mov eax, 55 ; fcntl (/usr/include/asm/unistd.h) int 80h test eax, eax ; ERROR js err ; ******************* send connect message ************************* mov eax, send1 ; pointer to connect message mov edx, send1l call get_xauth ; try to read .Xauthority jc _11 ; no success, let's try without auth. mov [send1+6], bx ; insert name length mov [send1+8], si ; insert data length call x_send ; send header mov eax, ecx ; pointer to name lea edx, [ebx + 3] ; pad to a multiple of 4 and edx, -4 call x_send ; send name mov eax, ebp ; pointer to data lea edx, [esi + 3] ; pad to a multiple of 4 and edx, -4 _11: call x_send ; send data xor ebp, ebp ; number of total bytes read mov esi, buf2 ; pointer to buffer for next read mov edi, buf2l ; max. bytes to read .10: mov eax, esi mov edx, edi call x_receive_raw jz .10 ; but we need a reply cmp byte [buf2], 1 ; success jne err ; something went wrong add ebp, eax ; total read bytes add esi, eax ; pointer to buffer for next read sub edi, eax ; max. bytes to read cmp ebp, 8 ; at least 8 bytes read? jc .10 ; no, get more movzx ebx, word [buf2 + 6] ; additional data in 4 bytes lea ebx, [ebx * 4 + 8] ; total size in bytes cmp ebp, ebx ; all read jc .10 ; no, get more ; ******************* calculate id's ******************************* mov esi, buf2 mov eax, [esi + 0Ch] ; resource_id_base mov edx, [esi + 10h] ; resource_id_mask mov ecx, edx neg ecx and edx, ecx ; resource_id_incr mov [s2a], eax ; wid for CreateWindow mov [s3a], eax ; wid for MapWindow mov [s4a], eax ; wid for CreateDC mov [s5a], eax ; wid for CreateDC mov [s6a], eax ; wid for SetInputFocus add eax, edx ; next id mov [s4b], eax ; cid for CreateDC mov [s5b], eax ; cid for CreateDC add eax, edx ; next id ; lint!!! ; mov [resource_id_next], eax ; mov [resource_id_incr], edx ; ******************* get root window id *************************** movzx eax, word [esi + 18h] ; length of vendor string add eax, 28h + 3 ; const header length + round vendor length and al, -4 ; round to 4 bytes movzx edx, byte [esi + 1Dh] ; number of FORMATs shl edx, 3 ; 8 byte for each FORMAT entry add edx, eax ; offset to root WINDOW id mov eax, [esi + edx] ; root window mov [s2b], eax ; CreateWindow needs root window id mov eax, [esi + edx + 20] ; width/height of root window mov [s2x], eax ; create window full size sub eax, (200 << 16) + 320 shr eax, 1 and eax, 0FFFF7FFFh mov [s5x], eax ; center drawing ; ******************* send CreatWindow request ********************* mov eax, send2 mov edx, send2l call x_send call x_receive jz .20 ; no message is a good message cmp byte [eax], 0 ; error message je ende ; ******************* send MapWindow request *********************** .20: mov eax, send3 mov edx, send3l call x_send call x_receive jz .30 ; no message is a good message cmp byte [eax], 0 ; error message je ende ; ******************* send CreatDC request ************************* .30: mov eax, send4 mov edx, send4l call x_send call x_receive jz .40 ; no message is a good message cmp byte [eax], 0 ; error message je ende ; ******************* send SetInputFocust ************************* .40: mov eax, send6 mov edx, send6l call x_send call x_receive jz .60 ; no message is a good message cmp byte [eax], 0 ; error message je ende .60: call init_color ; init 64 VGA colors ; ******************** main loop *************************** .50: call annie ; generate next picture call display call x_receive jz .50 ; no message is a good message cmp byte [eax], 0 ; error message je err cmp byte [eax], 2 ; key press je ende cmp byte [eax], 4 ; button press jne .50 err: ende: mov ebx, 0 ; return code mov eax, 1 ; exit int 80h ;------------------------------------------ display: mov esi, screen mov ecx, 20 ; we use 20 parts to make each less than 16k ..10 mov eax, send5 mov edx, send5l call x_send mov eax, esi mov edx, 320 * 10 * 4 ; size of one part call x_send add word [s5y], 10 ; update y pos for next part add esi, 320*10*4 ; update source pointer for next part loop .10 sub word [s5y], 20*10 ; restore original y position ret ;----------------------------------------- ; ********* Annie's code to draw a heart **************** annie: pusha xor ebx, ebx .10: inc dword [annie1] mov ecx, 320 * 200 xor edi, edi .20: mov eax, edi ; byte pos in screen xor edx, edx mov ebx, 320 ; 320 lines div ebx ; eax: line 0-199 edx: column 0-319 sub eax, 120 ; center y=120 (-120 .. +79) sub edx, 160 ; x=160 (-160 .. +159) jg .30 neg edx ; symmetric in x (0 .. 160) .30: mov ebx, eax imul ebx, ebx ; ebx = x*x add eax, edx ; eax = x*x+y imul eax ; eax = (x*x+y)**2 mod 2*16 add ebx, eax jz .40 xor edx, edx mov eax, 600000 div ebx .40: add eax, [annie1] ; change color shr al, 2 movzx eax, al mov eax, [color+ eax * 4] mov [screen + edi * 4], eax inc edi loop .20 popa nop ret ; ****************** initialize 64 VGA colors ********************* init_color: pusha mov esi, color mov eax, 0 ; sic mov ecx, 64 _01: mov [esi], eax add esi, 4 add al, 10h add ax, 800h add eax, 40000h loop _01 popa nop ret ;********************************************************** ;******** read cookie from $home/.Xauthority ************** ;********************************************************** ; * ; input: stack_ptr: original sp at program start * ; output: C=0: cookie found in $home/.Xauthority * ; r2: pointer to protocol name * ; r3: length of protocol name * ; r4: pointer to protocol data * ; r5: length of protocol data * ; C=1: nothing found * ; r2/r3/r4/r5 undefined * ; * ; typedef struct xauth { * ; unsigned short family; * ; unsigned short address_length; * ; char *address; * ; unsigned short number_length; * ; char *number; * ; unsigned short name_length; * ; char *name; * ; unsigned short data_length; * ; char *data; * ; } Xauth; * ;********************************************************** get_xauth: push eax push edx push edi mov edi, [stack_ptr] ; original stack pointer at program start mov eax, [edi] ; number of arguments lea edi, [edi + eax * 4 + 8] ; skip arguments + trailing null pointer .20: mov esi, [edi] ; pointer to next env variable add edi, 4 test esi, esi ; no more env variables jz .notfound cmp dword [esi], 'HOME' ; HOME found? jne .20 ; no, try next cmp byte [esi + 4], '=' ; HOME= found? jne .20 ; no, try next add esi, 5 ; start of HOME path or ecx, -1 .30: inc ecx ; count length of HOME path cmp byte [esi + ecx], 0 jne .30 or ecx, ecx ; at least one char long? jz .notfound ; no, HOME is empty cmp ecx, 256 ; more than 256 charcters ja .notfound ; somebody tries a buffer overflow mov edi, fname ; buffer for filename rep movsb ; copy HOME path mov eax, '/.Xa' ; 'aX./' ; add .Xauthority stosd mov eax, 'utho' ; 'ohtu' stosd mov eax, 'rity' ; 'ytir' stosd mov byte [edi], 0 ; and a trailing 0 mov ebx, fname xor ecx, ecx ; readonly mov eax, 5 ; open int 80h test eax, eax ; file open error? js .notfound ; yes mov ebx, eax ; file handle mov ecx, buf2 mov edx, buf2l ; read 1024 byte mov eax, 3 ; read int 80h cmp eax, buf2l jnc err ; .Xauthority >= 1024 byte mov ebp, eax ; bytes read mov eax, 6 ; close int 80h test ebp, ebp ; file empty jz .notfound mov esi, buf2 add ebp, esi ; end of read data xor eax, eax .60: lodsw ; family dec ax jz .40 ; 1=FamilyLocal mov ecx, 4 ; skip entry .50: lodsw ror ax, 8 ; big -> little endian add esi, eax loop .50 cmp esi, ebp ; more data jc .60 ; try next entry ..notfound: stc jmp _70 .40: mov ecx, 2 mov ebx, ecx .41: lodsw ror ax, 8 add esi, eax ; skip address/number loop .41 .42: lodsw ror ax, 8 mov ecx, esi mov ebx, eax add esi, ebx lodsw ror ax, 8 mov ebp, esi mov esi, eax clc _70: pop edi pop edx pop eax ret ;********************************************************** ;******** send message to X server ************** ;********************************************************** ; input: eax: pointer to message * ; edx: length of message * ;********************************************************** x_send: pusha mov ebp, eax ; pointer to next byte of message mov esi, edx ; remaining bytes to send .20: push 0 ; flags push esi ; length push ebp ; pointer to data push dword [x_handle] ; socket handle mov ecx, esp ; pointer to parameter for "send" mov ebx, 9 ; "send" (/usr/include/linux/net.h) mov eax, 102 ; socketcall (/usr/include/asm/unistd.h) int 80h add esp, 4*4 ; free space for parameters cmp eax, -11 ; EAGAIN: je .20 ; message couldn't be sent, try again test eax, eax ; ERROR js err sub esi, eax ; remaining bytes to send jz .30 ; nothing, all sent add ebp, eax ; pointer to remaining message jmp .20 ; send rest of message .30: popa nop ret ;********************************************************** ;******** receive ONE message from X server ********** ;********************************************************** ; input: none * ; output: Z=1: no complete message available * ; eax/edx undefined * ; Z=0: eax: pointer to message data * ; edx: size of data * ;********************************************************** x_receive: push ecx push esi push edi _00: mov eax, [buf2_rest] ; still something in read buffer? cmp eax, 32 ; a message has at least 32 bytes jnc .10 ; maybe it is a complete message .30: mov esi, [buf2_ptr] ; start of message mov edi, buf2 ; start of buffer mov [buf2_ptr], edi ; we copy message to top of buffer cmp edi, esi ; already at top of buffer je .50 ; then nothing to copy or eax, eax ; nothing in buffer jz .50 ; then also nothing to copy mov ecx, eax ; copy to top of buffer rep movsb .50: mov edx, buf2l ; let's try to get some more data sub edx, eax ; not more bytes than space is left in the buf lea eax, [buf2 + eax] ; append it here call x_receive_raw jnz .20 ; we could read something jmp _100 ; return with Z=1 .20: add [buf2_rest], eax ; now we have a few more bytes in the buffer jmp _00 ; let's try again .10: mov esi, [buf2_ptr] ; let's test if it is a complete meesage cmp byte [esi], 34 ja err ; the last known message is nr 34 mov edx, 32 ; cmp byte [esi], 0 ; error message ; je .40 cmp byte [esi], 1 ; reply message jne .40 ; event message is always 32 byte add edx, [esi + 12] ; + additional data for reply add edx, [esi + 12] ; + additional data for reply add edx, [esi + 12] ; + additional data for reply add edx, [esi + 12] ; + additional data for reply cmp eax, edx ; complete reply in buffer jc .30 ; no, let's try to get more .40: mov eax, esi ; pointer to data sub [buf2_rest], edx ; new rest add [buf2_ptr], edx ; pointer to next data; clear Z flag _100: pop edi pop esi pop ecx ret ;********************************************************** ;******** read data from X server ********** ;********************************************************** ; input: eax: pointer to read buffer * ; edx: size of buffer * ; output: Z=1: nothing to read * ; Z=0: eax bytes read * ;********************************************************** x_receive_raw: push ecx push ebx push 0 ; flags push edx ; bytes to read push eax ; pointer to buffer push dword [x_handle] ; socket handle mov ecx, esp ; pointer to parameter for "recv" mov ebx, 10 ; "recv" (/usr/include/linux/net.h) mov eax, 102 ; socketcall (/usr/include/asm/unistd.h) int 80h add esp, 4 * 4 ; free space for parameters pop ebx pop ecx cmp eax, -11 ; EAGAIN: no message available -> Z=1 je .10 test eax, eax ; <0: ERROR 0: NULL message -> Z=1 js err .10: ret ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;--------------------------- constant data --------------------------------- ; (note that we're in .text, not .rdata) align 4 sockaddr_un: dw 1 ; 1: AF_UNIX, AF_LOCAL (/usr/include/linux/socket.h) db "/tmp/.X11-unix/X0" sockaddr_un_l equ $ - sockaddr_un ;--------------------------------------------------------------------------- ;--------------------------------------------------------------------------- ;=========================================================================== ; end of code and constant data section ;=========================================================================== align 4 code_memsz equ $-$$ code_filez equ code_memsz data_addr equ (orig+code_memsz+4095)/4096*4096 + (code_filez % 4096) data_offset equ code_filez section .data vstart=data_addr ;=========================================================================== ;--------------------------- initialized data ------------------------------ buf2_ptr: dd buf2 buf2_rest: dd 0 ; Connection Setup send1: db $6c,0 ; LSB first dw 11,0 ; major/minor version dw 0,0 ; length of protocol name/data dw 0 ; unused send1l equ $ - send1 ; Create Window send2: db 1 ; opcode for Create Window db 0 ; depth from parent dw send2l/4; request length s2a: dd 0 ; wid (has to be calculated) s2b: dd 0 ; parent (has to be calculated) dw 0 ; x dw 0 ; y s2x: dw 640 ; width s2y: dw 400 ; heigth dw 0 ; border-width dw 0 ; class: CopyFromParent dd 0 ; visual: CopyFromParent dd 0A02h ; value-mask: background-pixel 2 ; + override-redirect 200 ; + event-mask 800 dd 0 ; background: black db 1 ; override-redirect = true db 0,0,0 ; pad dd 5 ; event_mask: KeyPress 1 ; +ButtenPress 4 ; +PointerMotion 40 send2l equ (($-send2)+3) & 0fffffffch ; Map Window send3: db 8 ; opcode for Map Window db 0 ; unused dw send3l/4; request length s3a: dd 0 ; wid (has to be calculated) send3l equ $ - send3 ; Create GC send4: db 55 ; opcode for CreateGC db 0 ; unused dw send4l/4; request length s4b: dd 0 ; cid (has to be calculated) s4a: dd 0 ; wid (has to be calculated) dd 1+4+8 ; function+foreground+background dd 3 ; function=copy dd 0ffffffh ; foreground: white dd 0080ffh ; background: light blue send4l equ $ - send4 ; Put Image send5: db 72 ; opcode for PutImage db 2 ; ZPixmap dw send5l/4 + 320*10*4/4 ; request length s5a: dd 0 ; wid (has to be calculated) s5b: dd 0 ; cid (has to be calculated) dw 320 ; width dw 200/20 ; height s5x: dw 0 ; dest-x s5y: dw 0 ; dest-y db 0 ; left-pad db 24 ; depth dw 0 ; unused send5l equ $ - send5 ; Set Input Focus send6: db 42 ; opcode for SetInputFocus db 0 ; revert-to None dw send6l/4; request length s6a: dd 0 ; wid (has to be calculated) dd 0 ; timestamp CurrentTime send6l equ $ - send6 ;=========================================================================== idat_memsz equ $-$$ bss_addr equ data_addr+ ($-$$) section .bss vstart=bss_addr ;=========================================================================== ;--------------------------- uninitialized data ---------------------------- screen: resd 320*200 ; bitmap stack_ptr: resd 1 x_handle: resd 1 annie1: resd 1 color: resd 64 fname: resb 256+32 buf2: resb 1024 buf2l equ $ - buf2 ;--------------------------------------------------------------------------- ;=========================================================================== udat_memsz equ $-$$ data_memsz equ idat_memsz + udat_memsz data_filez equ idat_memsz ;===========================================================================
From: Rod Pemberton on 28 Jul 2007 17:33 "Phil Carmody" <thefatphil_demunged(a)yahoo.co.uk> wrote in message news:873aze5gms.fsf(a)nonospaz.fatphil.org... > Well, it does say that ``la[--i]'' is to be evaluated before ``la[--i]=i''. True, that is stated. > It also says that ``--i'' is to be evalutate before ``la[--i]''. False, that is unstated. But, it is a logical corollary to 'la[--i]' being evaluated. > That much I evidently have no issue with. > > It does *not* say that ``la[--i]'' is to be evaluated before ``i''. > True, that is unstated. But, if it where stated, that would contradict conditions of 'la[--i]' being evaluated prior to 'la[--i]=i'. It says 'la[--i]' is to be evaluated before 'la[--i]=i'. I.e., '--i' must be evaluated prior to 'i' to maintain precedence: 7. Expressions "The precedence of expression operators is the same as the order of the major subsections of this section (highest precedence first). ... Otherwise the order of evaluation of expressions is undefined. In particular the compiler considers itself free to compute subexpressions in the order it believes most efficient, even if the subexpressions involve side effects." 7.1.5 "A primary expression followed by an expression in square brackets is a primary expression."... 7.14.1 lvalue = expression "The value of the expression replaces that of the object referred to by the lvalue."... Rod Pemberton
From: Phil Carmody on 29 Jul 2007 05:54
"Rod Pemberton" <do_not_have(a)nowhere.cmm> writes: > "Phil Carmody" <thefatphil_demunged(a)yahoo.co.uk> wrote in message > news:873aze5gms.fsf(a)nonospaz.fatphil.org... > > Well, it does say that ``la[--i]'' is to be evaluated before > ``la[--i]=i''. > > True, that is stated. > > > It also says that ``--i'' is to be evalutate before ``la[--i]''. > > False, that is unstated. But, it is a logical corollary to 'la[--i]' being > evaluated. > > > That much I evidently have no issue with. > > > > It does *not* say that ``la[--i]'' is to be evaluated before ``i''. > > > > True, that is unstated. But, if it where stated, that would contradict > conditions of 'la[--i]' being evaluated prior to 'la[--i]=i'. > > > It says 'la[--i]' is to be evaluated before 'la[--i]=i'. I.e., '--i' must > be evaluated prior to 'i' to maintain precedence: Utter utter nonsense. Your "i.e." contains no valid logic at all. > 7. Expressions > "The precedence of expression operators is the same as the order of the > major subsections of this section (highest > precedence first). ... Otherwise the order of evaluation of expressions is > undefined. In particular the compiler considers itself free to > compute subexpressions in the order it believes most efficient, even if the > subexpressions involve side effects." > > 7.1.5 > "A primary expression followed by an expression in square brackets is a > primary expression."... And? > 7.14.1 lvalue = expression > "The value of the expression replaces that of the object referred to by the > lvalue."... And? I'm failing to see the "`lvalue' is evaluated before 'expression'" in the above. If it said that, you'd have a point. It doesn't, for a reason, and you don't, for a reason too. The only thing relevant in the above is the fact that it clearly says that where orders aren't specified otherwise, then they undefined, which blows your whole argument out of the water. And you've not worked out my teaser yet either I notice. Phil -- "Home taping is killing big business profits. We left this side blank so you can help." -- Dead Kennedys, written upon the B-side of tapes of /In God We Trust, Inc./. |