为什么 0x90 在 Eclipse 2021-03 CDT - C 代码中作为参数变为 0xFF (255)？

Question

我正在构建一个名为 Open SAE J1939 的 J1939 项目，用于工业 Can 总线系统，我注意到 Eclipse CDT.

有一些奇怪的地方

我调用函数

ENUM_J1939_STATUS_CODES SAE_J1939_Send_Request_Address_Claimed(J1939 *j1939, uint8_t DA)

请注意我正在使用 uint8_t DA = 0x90 = 144

为什么我在这里得到 DA = 0xFF = 255？这是 Eclipse CDT 2021-03 中的错误吗？

重现此问题。只需下载库和运行 Main.c 文件。这个。

#include "stdlib.h"
#include "stdio.h"

/* Our includes */
#include "Open SAE J1939/Open_SAE_J1939.h"
#include "SAE J1939-71 Application Layer/SAE_J1939-71_Application_Layer.h"
#include "SAE J1939-73 Diagnostics Layer/SAE_J1939-73_Diagnostics_Layer.h"
#include "SAE J1939-81 Network Management Layer/SAE_J1939-81_Network_Management_Layer.h"
#include "ISO 11783 Tractors And Machinery For Agriculture And Forestry/ISO 11783-7 Implement Messages Application Layer/ISO_11783_7_Implement_Messages_Application_Layer.h"


int main() {

    /* Create our J1939 structure with two ECU */
    J1939 j1939_1;
    J1939 j1939_2;

    /* Important to set all to 0 */
    memset(&j1939_1, 0, sizeof(j1939_1));
    memset(&j1939_2, 0, sizeof(j1939_2));

    /* Set the ECU address */
    j1939_1.this_ECU_address = 0x80;                                                /* From 0 to 253 because 254 = error address and 255 = broadcast address */
    j1939_2.this_ECU_address = 0x90;

    /* Set NAME for ECU 1 */
    j1939_1.this_name.identity_number = 100;                                        /* From 0 to 2097151 */
    j1939_1.this_name.manufacturer_code = 300;                                      /* From 0 to 2047 */
    j1939_1.this_name.function_instance = 10;                                       /* From 0 to 31 */
    j1939_1.this_name.ECU_instance = 2;                                             /* From 0 to 7 */
    j1939_1.this_name.function = FUNCTION_VDC_MODULE;                               /* From 0 to 255 */
    j1939_1.this_name.vehicle_system = 100;                                         /* From 0 to 127 */
    j1939_1.this_name.arbitrary_address_capable = 0;                                /* From 0 to 1 */
    j1939_1.this_name.industry_group = INDUSTRY_GROUP_CONSTRUCTION;                 /* From 0 to 7 */
    j1939_1.this_name.vehicle_system_instance = 10;                                 /* From 0 to 15 */

    /* Set NAME for ECU 2 */
    j1939_2.this_name.identity_number = 1000;                                       /* From 0 to 2097151 */
    j1939_2.this_name.manufacturer_code = 400;                                      /* From 0 to 2047 */
    j1939_2.this_name.function_instance = 20;                                       /* From 0 to 31 */
    j1939_2.this_name.ECU_instance = 1;                                             /* From 0 to 7 */
    j1939_2.this_name.function = FUNCTION_AUXILIARY_VALVES_CONTROL;                 /* From 0 to 255 */
    j1939_2.this_name.vehicle_system = 50;                                          /* From 0 to 127 */
    j1939_2.this_name.arbitrary_address_capable = 0;                                /* From 0 to 1 */
    j1939_2.this_name.industry_group = INDUSTRY_GROUP_AGRICULTURAL_AND_FORESTRY;    /* From 0 to 7 */
    j1939_2.this_name.vehicle_system_instance = 15;                                 /* From 0 to 15 */

    /* Broadcast NAME from ECU 1 */
    SAE_J1939_Send_Request_Address_Claimed(&j1939_1, 0x90);                         /* Request ECU NAME from ECU 2 */

    /* Listen for messages at ECU 2 */
    Open_SAE_J1939_Listen_For_Messages(&j1939_2);

    /* Send NAME from ECU 2 to ECU 1 */
    SAE_J1939_Send_Request_Address_Claimed(&j1939_2, 0x80);                         /* Request ECU NAME from ECU 1 */

    /* Listen for messages at ECU 1 */
    Open_SAE_J1939_Listen_For_Messages(&j1939_1);

    /* Print information */
    printf("How many external ECU are connected according to ECU 1? %i\n", j1939_1.number_of_ECU);
    printf("How many external ECU are connected according to ECU 2? %i\n", j1939_2.number_of_ECU);


    return 0;
}

Answer 1

很可能您是编译器优化的受害者。底层调试器向您显示某些寄存器或内存的内容，但真正的值在其他地方，如果下一次调用完成，它将被安排。哦，对 SAE_J1939_Send_Request() 的调用可能只是为了节省时钟周期而跳转，因为这是最后一次调用，而你 return 它的 return 值。

请查看反汇编，并遵循该级别的值。

另一种选择是降低优化级别。

顺便说一句，这与 Eclipse 无关。这是一个 compiler/debugger 问题。

为什么 0x90 在 Eclipse 2021-03 CDT - C 代码中作为参数变为 0xFF (255)？

Why does 0x90 become 0xFF (255) as a argument i Eclipse 2021-03 CDT - C code?

c

eclipse

eclipse-cdt

can-bus