Function with weak atributte can not be overwritten - c++

Question

I would like to overwrite function (interupt handlers) with the weak attribute, but linker does not link my definition. Codes are shorted for better reading.
vectors.c
void NMI_Handler (void) __attribute__((weak));
void HardFault_Handler (void) __attribute__((weak));
__attribute__ ((section(".vectors"), used))
void (* const gVectors[])(void) =
{
NMI_Handler,
HardFault_Handler
};
void NMI_Handler (void) { while(1); }
void HardFault_Handler (void) { while(1); }
I redefine default definition in the file cpuexcept.cpp
extern "C" __attribute__((naked))
void NMI_Handler()
{
EXCEPT_ENTRY(CPUExcept);
}
extern "C" __attribute__((naked))
void HardFault_Handler()
{
EXCEPT_ENTRY(CPUExcept);
}
If I compile and dump it, output (library lib.a) is:
cpuexcept.oo: file format elf32-littlearm
rw-rw-rw- 0/0 4728 Jun 26 16:20 2012 cpuexcept.oo
architecture: arm, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
private flags = 5000000: [Version5 EABI]
Sections:
Idx Name Size VMA LMA File off Algn Flags
0 .text 0000051c 00000000 00000000 00000034 2**2 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 00000000 00000000 00000550 2**0 CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000550 2**0 ALLOC
3 .rodata 000001dc 00000000 00000000 00000550 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .comment 00000012 00000000 00000000 0000072c 2**0 CONTENTS, READONLY
5 .ARM.attributes 00000031 00000000 00000000 0000073e 2**0 CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 cpuexcept.cpp
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
000004e0 g F .text 0000000a NMI_Handler
000004ec g F .text 0000000a HardFault_Handler
000004e0 <NMI_Handler>:
4e0: e92d 0ff0 stmdb sp!, {r4, r5, r6, r7, r8, r9, sl, fp}
4e4: 4668 mov r0, sp
4e6: f7ff fffe bl c0 <CPUExcept> 4e6: R_ARM_THM_CALL CPUExcept
4ea: bf00 nop
000004ec <HardFault_Handler>:
4ec: e92d 0ff0 stmdb sp!, {r4, r5, r6, r7, r8, r9, sl, fp}
4f0: 4668 mov r0, sp
4f2: f7ff fffe bl c0 <CPUExcept> 4f2: R_ARM_THM_CALL CPUExcept
4f6: bf00 nop
vectors.o: file format elf32-littlearm
rw-rw-rw- 0/0 4464 Jun 27 13:52 2012 vectors.o
architecture: arm, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
private flags = 5000000: [Version5 EABI]
Sections:
Idx Name Size VMA LMA File off Algn Flags
0 .text 00000114 00000000 00000000 00000034 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .data 00000000 00000000 00000000 00000148 2**0 CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 00000000 00000000 00000148 2**0 ALLOC
3 .vectors 00000130 00000000 00000000 00000148 2**2 CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
4 .comment 00000012 00000000 00000000 00000278 2**0 CONTENTS, READONLY
5 .ARM.attributes 00000031 00000000 00000000 0000028a 2**0 CONTENTS, READONLY
SYMBOL TABLE:
00000000 l df *ABS* 00000000 vectors.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .vectors 00000000 .vectors
00000000 l d .comment 00000000 .comment
00000000 l d .ARM.attributes 00000000 .ARM.attributes
00000000 w F .text 00000002 NMI_Handler
00000004 w F .text 00000002 HardFault_Handler
00000000 <NMI_Handler>:
0: e7fe b.n 0 <NMI_Handler>
2: bf00 nop
00000004 <HardFault_Handler>:
4: e7fe b.n 4 <HardFault_Handler>
6: bf00 nop
Default function with the weak attribute is linked in to target application. My definition is linked correct, if I define function f() in cpuexcept.cpp and I use it in main function or if my definiton of handler is in other .c module.
I use arm-none-eabi-gcc 4.6.2 (YAGARTO) compiler in cygwin.

Answer 1

You could try to define your function like
void NMI_Handler(void)
and not as
void NMI_Handler()
As the weak definition is also void NMI_Handler (void) __attribute__((weak));
So the linker will not see any difference.