SDK 14 buttonless dfu not building with gcc

[jithin m das]

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

[jithin m das]

Downgrading arm gcc from 5.4.1 to 4.9.3 solved the issue.

[idelsink]

Well the issue is still not solved, because just simply downgrading it is not a solve for any problem.

[bjorn-spockeli]

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"                               \

[Omead]

Doing this, however, breaks the buttonless DFU application template's operation. Downgrading gcc to 4.9 seems to produce the correct code.

[bjorn-spockeli]

@oamidi: Thanks for letting us know. The SDK is production tested using GCC v4.9.3, so that is the recommended solution.