Eclipse CDT 中未定义的函数引用答案

【问题标题】：undefined reference to function in Eclipse CDTEclipse CDT 中未定义的函数引用
【发布时间】：2015-05-09 18:28:16
【问题描述】：

在我的main.c 程序中，我包含了这个库：

#include "coap_api.h"

这也包含在 Properties -> C/C++ Build -> Settings -> Cross ARM GNU Assembler -> Includes

和

Properties -> C/C++ Build -> Settings -> Cross ARM C Compiler -> Includes

构建项目时出现此错误：

./src/main.o: In function `main':
/Users/joanet/Development/Embedded/eclipseWS/EHAL-master/ARM/Nordic/nRF51/ipv6_coap_server/Release/../src/main.c:708: undefined reference to `coap_init'

我在另一篇文章中读到我必须链接库 (http://whatwouldnickdo.com/wordpress/328/eclipse-cdt-and-linux-libraries/)

我尝试添加名称为 coap_api 的库，但我不工作

lib/gcc/arm-none-eabi/4.9.3/../../../../arm-none-eabi/bin/ld: cannot find -lcoap_api

在编译中包含 coap 目录：

arm-none-eabi-gcc -mcpu=cortex-m0 -mthumb -Os -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wall  -g -DBLE_STACK_SUPPORT_REQD -DNRF51 -D__CORTEX_M0 -DBOARD_PCA10028 -DSOFTDEVICE_PRESENT -DS110 -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/ipv6_coap_server/bsp -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/iot/ipv6_stack/pbuffer -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/util/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/drivers_nrf/hal/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/../../../ARM/CMSIS/CMSIS/Include/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/../../../ARM/Nordic/nRF51/CMSIS/include/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/softdevice/s110/headers/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/common/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_bas/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_dis/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/device_manager/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/softdevice/common/softdevice_handler/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/scheduler/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_error_log/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/drivers_nrf/ble_flash/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_debug_assert_handler/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/timer/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/gpiote/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/drivers_nrf/pstorage/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_dfu/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/bootloader_dfu/experimental/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/bootloader_dfu/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/../../../include/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_hids/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/../../../ARM/CMSIS/CMSIS_RTX/INC/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/trace/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/device/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_tps/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/button/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/device_manager/config/" -I"/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/ipv6_coap_client/src" -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/toolchain/gcc -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/libraries/mem_manager -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/ble/ble_services/ble_ipsp -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/iot/include -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/iot/ipv6_stack/include -I/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/nrf51_sdk/components/iot/coap -std=gnu99 -MMD -MP -MF"src/Vectors_nRF51.d" -MT"src/Vectors_nRF51.o" -c -o "src/Vectors_nRF51.o" "/Users/nullpointer/Development/Embedded/eclipseWS/EHAL-master-Hoan/ARM/Nordic/nRF51/src/Vectors_nRF51.c"

【问题讨论】：

错误是由 GNU 链接器产生的； EclipseCDT 与它关系不大。发布完整的构建日志，显示正在执行的命令行，而不仅仅是错误。
在哪里可以看到构建日志？在控制台中？
我不知道；我不使用 Eclipse；但它肯定在某处可用 - 可能是您阅读这些错误的任何地方的整个文本。上下文很有用，更适合用于查看构建正在做什么，而不是您描述它。

标签： c embedded eclipse-cdt toolchain gnu-toolchain

【解决方案1】：

行：

#include "coap_api.h"

不包括库，它包括一个包含在别处定义的声明的头文件。您确实必须链接包含这些定义的单独编译的目标代码。

如果这是一个库文件，您需要以与包含路径类似的方式设置库路径。如果库的名称为 GNU 常规形式 libXXX.a，则它与开关 -lXXX 链接，否则您必须指定完整的文件名。

但是，如果 coap_api.h 中的声明引用源代码形式的定义，那么您必须将源代码添加到您的项目中以进行单独的编译和链接。

【讨论】：

它在另一个 c 程序 (coap.c) 中，包含在 Properties -> C/C++ Build -> Settings -> Cross ARM GNU Assembler -> Includes and Properties -> C/C++ Build - > 设置 -> Cross ARM C 编译器 -> 包含
那不是“另一个程序”，它是你的程序中的一个单独的翻译单元。它不应该被“包含”，它应该被编译一个链接。项目包含设置应仅指定目录路径，而不是实际文件。
是的，包括coap.c和coap_api.h所在的目录
库路径用于搜索 .a（存档）文件，我认为也是 .o（目标文件），将其指向 .c 文件将无效；在这种情况下，您必须将它添加到您的项目中以便与 main.c 一起编译，或者单独构建一个库。因此，我的回答的最后一段适用。这是完整的构建日志有用的诊断。

【解决方案2】：

您需要从 coap.c 链接生成目标文件，然后从这个 .o 制作一个库，或者使用这个之前生成的 coap.o 文件直接编译您的项目。

您应该阅读一些有关编译和链接的文档。在这里，您的编译器告诉您它对coap_init 有未定义的引用，这实际上是由您的程序调用并由coap_api.h 文件引用。问题是它找不到相关的机器代码。您可能已经包含了 coap.c 目录，它只不过是一个文本文件。您首先需要编译它，然后创建一个链接到项目的库，或者复制导入项目中的 coap.c，以便它与您的其余工作一起编译。

【讨论】：