I'm using SDK 14 and trying to build the ble_app_buttonless_dfu example. I'm using Linux environment, so gcc for building. When I try to build the example I'm getting an error as below,
Compiling file: ble_dfu_unbonded.c
/tmp/cchirqL7.s: Assembler messages:
/tmp/cchirqL7.s:64: Error: cannot honor width suffix -- `ldr.w r12,=#3'
make: *** [_build/nrf52832_xxaa/ble_dfu_unbonded.c.o] Error 1
Please suggest a solution
The compiler is complaining about the following function in nrf_svci.h
#define SVCI_DECL(svci_num, return_type, function_name, ...) \
_Pragma("GCC diagnostic push") \
_Pragma("GCC diagnostic ignored \"-Wreturn-type\"") \
__attribute__((naked, unused)) \
static return_type svci_ ## function_name(__VA_ARGS__) \
{ \
/* Do the SuperVisor call by using svc instruction with \
R12 containing the SVCI number */ \
__ASM __volatile \
( \
" ldr.w r12, =%0 \n" \
" svc %1 \n" \
" bx lr \n" \
" .ltorg" \
: /* output */ \
: /* input */ \
"X"(svci_num), \
"I"(GCC_CAST_CPP NRF_SVCI_SVC_NUM) \
: /* clobbers */ \
"r12" \
); \
} \
_Pragma("GCC diagnostic pop")
Specifically, its the optional instruction width specifier .w, which forces the LDR to generate a 32-bit instruction in Thumb-2 code, according to this Stack Overflow post. Removing this optional specifier, i.e. leaving it t the compiler to decide the instruction width seems to do the trick ,i.e.
" ldr r12, =%0 \n" \
The compiler is complaining about the following function in nrf_svci.h
#define SVCI_DECL(svci_num, return_type, function_name, ...) \
_Pragma("GCC diagnostic push") \
_Pragma("GCC diagnostic ignored \"-Wreturn-type\"") \
__attribute__((naked, unused)) \
static return_type svci_ ## function_name(__VA_ARGS__) \
{ \
/* Do the SuperVisor call by using svc instruction with \
R12 containing the SVCI number */ \
__ASM __volatile \
( \
" ldr.w r12, =%0 \n" \
" svc %1 \n" \
" bx lr \n" \
" .ltorg" \
: /* output */ \
: /* input */ \
"X"(svci_num), \
"I"(GCC_CAST_CPP NRF_SVCI_SVC_NUM) \
: /* clobbers */ \
"r12" \
); \
} \
_Pragma("GCC diagnostic pop")
Specifically, its the optional instruction width specifier .w, which forces the LDR to generate a 32-bit instruction in Thumb-2 code, according to this Stack Overflow post. Removing this optional specifier, i.e. leaving it t the compiler to decide the instruction width seems to do the trick ,i.e.
" ldr r12, =%0 \n" \
Doing this, however, breaks the buttonless DFU application template's operation. Downgrading gcc to 4.9 seems to produce the correct code.
@oamidi: Thanks for letting us know. The SDK is production tested using GCC v4.9.3, so that is the recommended solution.
Is there a version of the SDK planned that will work with gcc 5.3.1 or later? We had to upgrade our codebase for a different reason and are now unable to use this DFU application.
If there's no update planned that will upgrade the supported gcc version, are there any other ideas for a solution (since the one above seems to have issues)?