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problem

treethink what tree

i use keil arm rvct
and have small problem
RVCT have no #pragma pack(1)
but when i got program from my friend i didnt see this program and RVCT didnt say warning about this command - and i have problem
because this command destroy execute program
for example

#pragma pack(1)

typedef struct
{ unsigned char command; unsigned long packets; unsigned char reserved[3];

} COMMAND2;

int main()
{ COMMAND2 cmd2; unsigned long Size;

cmd2.command = 0x01; cmd2.packets = 1000; Size = cmd2.packets; Size = cmd2.command;
}

when run this program Size <> 1 at the end !!!

undetermine command #pragma pack(1) create error and compiler dont say warning about this command
if correct program for RVTC

typedef __packed struct
{ unsigned char command; unsigned long packets; unsigned char reserved[3];

} COMMAND2;

int main()
{ COMMAND2 cmd2; unsigned long Size;

cmd2.command = 0x01; cmd2.packets = 1000; Size = cmd2.packets; Size = cmd2.command;
}

we will get ok result

Parents Reply Children
  • 0 in reply to Dan Henry

    ****************************************************
    IDE-Version:
    µVision3 V3.50
    Copyright (c) Keil Elektronik GmbH / Keil Software, Inc. 1995 - 2007

    Tool Version Numbers:
    Toolchain Path: BIN30\
    C Compiler: ARM/Thumb C/C++ Compiler, RVCT3.0 [Build 951] for uVision [Full]
    Assembler: ARM/Thumb Macro Assembler, RVCT3.0 [Build 951] for uVision [Full]
    Linker/Locator: ARM Linker, RVCT3.0 [Build 951] for uVision [Full]
    Librarian: ARM Archiver, RVCT3.0 [Build 951] for uVision
    Hex Converter: ARM FromELF, RVCT3.0 [Build 951] for uVision [Full]
    CPU DLL: SARM.DLL V3.04
    Dialog DLL: DARMP.DLL V1.13
    Target DLL: BIN\UL2ARM.DLL V1.26
    Dialog DLL: TARMP.DLL V1.11f
    ******************************************************

    would you like?
    please
    look at IMPORTANT 17 OPERATOR 17: cmd2.packets = 1000;

    ****************************************************

    #pragma pack(1)
    12: {
    13:         COMMAND2 cmd2;
    14:         unsigned long Size;
    15:
0x000001B0  E24DD008  SUB       R13,R13,#0x00000008
    16:         cmd2.command = 0x01;
0x000001B4  E3A00001  MOV       R0,#0x00000001
0x000001B8  E5CD0000  STRB      R0,[R13]
    17:         cmd2.packets = 1000;
0x000001BC  E3A00FFA  MOV       R0,#0x000003E8
0x000001C0  E28DC001  ADD       R12,R13,#0x00000001
0x000001C4  E58C0000  STR       R0,[R12]
    18:         Size = cmd2.packets;
0x000001C8  E28DC001  ADD       R12,R13,#0x00000001
0x000001CC  E59C1000  LDR       R1,[R12]
    19:         Size = cmd2.command;
    20:
    21:
0x000001D0  E5DD1000  LDRB      R1,[R13]
    22: }
*****************************************************************
if
typedef __packed struct
{
        unsigned char command;
    unsigned long packets;
    unsigned char reserved[3];

} COMMAND2;
    12: {
    13:         COMMAND2 cmd2;
    14:         unsigned long Size;
    15:
0x000001B0  E92D401C  STMDB     R13!,{R2-R4,R14}
    16:         cmd2.command = 0x01;
0x000001B4  E3A00001  MOV       R0,#0x00000001
0x000001B8  E5CD0000  STRB      R0,[R13]
    17:         cmd2.packets = 1000;
0x000001BC  E28D1001  ADD       R1,R13,#0x00000001
0x000001C0  E3A00FFA  MOV       R0,#0x000003E8
0x000001C4  EB00000E  BL        0x00000204
    18:         Size = cmd2.packets;
0x000001C8  E28D0001  ADD       R0,R13,#0x00000001
0x000001CC  EB000004  BL        0x000001E4
0x000001D0  E1A04000  MOV       R4,R0
    19:         Size = cmd2.command;
    20:
    21:
0x000001D4  E5DD4000  LDRB      R4,[R13]
    22: }
************************************************************************
have no #pragma
only for example what must be when compiler will be ignore #pragma

    12: {
    13:         COMMAND2 cmd2;
    14:         unsigned long Size;
    15:
0x000001B0  E24DD00C  SUB       R13,R13,#0x0000000C
    16:         cmd2.command = 0x01;
0x000001B4  E3A00001  MOV       R0,#0x00000001
0x000001B8  E5CD0000  STRB      R0,[R13]
    17:         cmd2.packets = 1000;
0x000001BC  E3A00FFA  MOV       R0,#0x000003E8
0x000001C0  E58D0004  STR       R0,[R13,#0x0004]
    18:         Size = cmd2.packets;
0x000001C4  E59D1004  LDR       R1,[R13,#0x0004]
    19:         Size = cmd2.command;
    20:
    21:
0x000001C8  E5DD1000  LDRB      R1,[R13]
    22: }

  • 0 in reply to test test

    "look at IMPORTANT 17 OPERATOR 17: cmd2.packets = 1000;"

    Ah, very good. That wasn't too hard, was it? You have finally shown what the problem is.

    For whatever ARM you are using or simulating, read up on how it handles unaligned memory accesses.

  • 0 in reply to Dan Henry

    "Ah, very good. That wasn't too hard, was it? You have finally shown what the problem is.

    For whatever ARM you are using or simulating, read up on how it handles unaligned memory accesses "

    are you top manager?
    who may see - will be see

    i finished this topic
    good bye baby ;-)

  • 0 in reply to test test

    "i finished this topic
    good bye baby"

    It is quite unusual to use such terms of endearment in a technical forum, but in case it is the custom where you are from:

    Good-bye dear.