SES 6.32: Strange behaviour

[cmag]

I am experiencing a strange behavior with SES 6.32, using GCC and I wonder if I should choose a different compiler.

COMPILING THIS PART OF CODE (I added line numbers for reference)

342 static void gap_params_init(void)
343 {
344    ret_code_t err_code;
345    ble_gap_conn_params_t gap_conn_params;
346    ble_gap_conn_sec_mode_t sec_mode;
347
348    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);
349
350    err_code = sd_ble_gap_device_name_set(&sec_mode,
351                                          (const uint8_t *)cfgGetDeviceName(),
352                                          strlen(cfgGetDeviceName()));

USING MY RELEASE CONFIGURATION

<configuration Name="Release"
   c_preprocessor_definitions="NDEBUG"
   gcc_debugging_level="None"
   gcc_optimization_level="Level 1" />

--- main.c -- 346 ------------------------------------------
ble_gap_conn_sec_mode_t sec_mode;
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);
err_code = sd_ble_gap_device_name_set(&sec_mode,
F001FEF6 bl 0x00029278 <cfgGetDeviceName>
4604     mov r4, r0
F001FEF3 bl 0x00029278 <cfgGetDeviceName>
F011FEEF bl 0x00039274 <strlen>
B282     uxth r2, r0
4621     mov r1, r4
A801     add r0, sp, #4
F7FFFFA2 bl 0x000273E4 <sd_ble_gap_device_name_set>

No trace of BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);

USING MY DEBUG CONFIGURATION

<configuration Name="Debug"
   c_preprocessor_definitions="DEBUG"
   gcc_debugging_level="Level 3"
   gcc_optimization_level="None" />

--- main.c -- 344 ------------------------------------------
ret_code_t err_code;
ble_gap_conn_params_t gap_conn_params;
ble_gap_conn_sec_mode_t sec_mode;
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);
F89D3004 ldrb.w r3, [sp, #4]
2201     movs r2, #1
F3620303 bfi r3, r2, #0, #4
F88D3004 strb.w r3, [sp, #4]
F89D3004 ldrb.w r3, [sp, #4]
2201     movs r2, #1
F3621307 bfi r3, r2, #4, #4
F88D3004 strb.w r3, [sp, #4]
--- main.c -- 349 ------------------------------------------
err_code = sd_ble_gap_device_name_set(&sec_mode,
(const uint8_t *)cfgGetDeviceName(),
F003FC76 bl 0x0002B0B8 <cfgGetDeviceName>
4604     mov r4, r0
--- main.c -- 352 ------------------------------------------
strlen(cfgGetDeviceName()));
F003FC73 bl 0x0002B0B8 <cfgGetDeviceName>
4603     mov r3, r0
4618     mov r0, r3
F023F857 bl 0x0004A888 <strlen>
4603     mov r3, r0
--- main.c -- 350 ------------------------------------------
err_code = sd_ble_gap_device_name_set(&sec_mode,
B29A     uxth r2, r3
AB01     add r3, sp, #4
4621     mov r1, r4
4618     mov r0, r3
F7FFFF7C bl 0x000276E0 <sd_ble_gap_device_name_set>
9007     str r0, [sp, #28]

Not even constant folding, but the code works.

USING MY RELEASE CONFIGURATION AGAIN
<configuration Name="Release"
   c_preprocessor_definitions="NDEBUG"
   gcc_debugging_level="None"
   gcc_optimization_level="Level 1" />

BUT
REPLACING: ble_gap_conn_sec_mode_t sec_mode;
WITH : static ble_gap_conn_sec_mode_t sec_mode;

--- main.c -- 348 ------------------------------------------
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);
B510     push {r4, lr}
4C17     ldr r4, =0x20008688 <sec_mode.5>
B084     sub sp, sp, #16
2311     movs r3, #17
7023     strb r3, [r4]
--- main.c -- 349 ------------------------------------------
err_code = sd_ble_gap_device_name_set(&sec_mode,
F002FB1F bl 0x00029A40 <cfgGetDeviceName>
9001     str r0, [sp, #4]
F002FB1C bl 0x00029A40 <cfgGetDeviceName>
F015FC4C bl 0x0003CCA4 <strlen>
9901     ldr r1, [sp, #4]
B282     uxth r2, r0
4620     mov r0, r4
F7FFFFE7 bl 0x000273E4 <sd_ble_gap_device_name_set>

I have no clue about this behavior of the compiler; is someone experiencing the same problem?

I am using GCC; is any other compiler (SEGGER, SEGGER-NG or CLANG) better?

[cmag]

My mistake: the call was by reference, so the register overwritten is not the problem.

Still there is a difference when calling the Softdevice function defined as follows (a few excerpts):

#define SVCALL(number, return_type, signature) \
_Pragma("GCC diagnostic push") \
_Pragma("GCC diagnostic ignored \"-Wreturn-type\"") \
__attribute__((naked)) \
__attribute__((unused)) \
static return_type signature \
{ \
__asm( \
"svc %0\n" \
"bx r14" : : "I" (GCC_CAST_CPP number) : "r0" \
); \
} \
_Pragma("GCC diagnostic pop")

SVCALL(SD_BLE_GAP_DEVICE_NAME_SET, uint32_t, sd_ble_gap_device_name_set(ble_gap_conn_sec_mode_t const *p_write_perm, uint8_t const *p_dev_name, uint16_t len));

With the following line of code:

err_code = sd_ble_gap_device_name_set(&sec_mode, (const uint8_t *)cfgGetDeviceName(), 
                                      strlen(cfgGetDeviceName()));

R0 point to sec_mode:

R0: 0x2003ff8c -> 07 79

And calling a function with a standard C signature:

__attribute__ ( (noinline))
uint32_t sd_ble_gap_device_name_set0(ble_gap_conn_sec_mode_t const *p_write_perm, uint8_t const *p_dev_name, uint16_t len)

{
sd_ble_gap_device_name_set0test = *p_write_perm;
}

With the following line of code:

err_code = sd_ble_gap_device_name_set0(&sec_mode, (const uint8_t *)cfgGetDeviceName(),
                                       strlen(cfgGetDeviceName()));

R0 points to sec_mode:

R0: 0x2003ff8c -> 11 0C

But the time the correct value is stored in memory.

So maybe it is an incompatibility between the compiler and the library. It seems that the compiler still tries to pass &sec_mode in R0 (I do not know if this is correct with SVCALL) but the fails to initialize sec_mode.

I will try to recompile with the latest library to check if this solves the problem.

[Einar Thorsrud]

Hi,

All SoftDevice API calls are SVC calls, so you should not compare with normal function calls.

I am still unsure about what the issue issue is and why you are digging into this, though? What is not working? Which problem are you trying to solve?