MK60 KDS 3.x Cross ARM compiler question

[henrynguyen]

Hi All,

we used Keil on Cortex M3 project in the past and able to declare the packed typedef struct as:

typedef __pack struct
{
BYTE byPriority;
BYTE byMsgType;
BYTE bySrcDvc;
BYTE byDstDvc;
WORD wPointer;
BYTE *byBuffer;
} CAN_BUFFER;

then, now we are using KDS 3.x and Cross ARM C compiler.  I have changed the typedef to the following 

typedef struct
{
BYTE byPriority;
BYTE byMsgType;
BYTE bySrcDvc;
BYTE byDstDvc;
WORD wPointer;
BYTE *byBuffer;
} CAN_BUFFER __attribute__((packed));

however, the compiler kicked out the warning message bold highlighted below:

Building file: ../Sources/main.c
Invoking: Cross ARM C Compiler
arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O0 -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -g3 -I"D:/ThruBit/GitRepositories/GIT_WS_KDS_New/MLSB_v1.0.0/Static_Code/PDD" -I"D:\ThruBit\GitRepositories\GIT_WS_KDS_New\MLSB_v1.0.0\Sources\Lib_Core" -I"D:\ThruBit\GitRepositories\GIT_WS_KDS_New\MLSB_v1.0.0\Sources\Lib_ComProtocol" -I"D:/ThruBit/GitRepositories/GIT_WS_KDS_New/MLSB_v1.0.0/Static_Code/IO_Map" -I"D:/ThruBit/GitRepositories/GIT_WS_KDS_New/MLSB_v1.0.0/Sources" -I"D:/ThruBit/GitRepositories/GIT_WS_KDS_New/MLSB_v1.0.0/Generated_Code" -std=c99 -MMD -MP -MF"Sources/main.d" -MT"Sources/main.o" -c -o "Sources/main.o" "../Sources/main.c"
In file included from ../Sources/main.c:49:0:
D:\GitRepositories\GIT_WS_KDS_New\MLSB_v1.0.0\Sources\Lib_ComProtocol/CanProtocol.h:73:1: warning: 'packed' attribute ignored [-Wattributes]  <<<<<<< warnning here
} CAN_BUFFER __attribute__((packed));

can you please help me understand the correct way to declare a packed typedef struct?

what is the meaning of "warning: 'packed' attribute ignored [-Wattributes]"?

Thanks,

Henry

[henrynguyen]

wow, i searched and found this link posted the solution by Mark Butcher:

https://community.nxp.com/message/846440?commentID=846440#comment-846440 

i tried it and it work for me.

Thanks,

Henry