Cortex-M3 (EFM32GG) - Newlib-Nano 的 ARM-GCC 链接器标志

Question

我分析了一个由 Simplicity Studio 生成的项目（Silicon Labs 的 Eclipse IDE 变体，用于他们的微控制器）。

我为基于 arm-none-eabi-gcc 工具链的 ASM/C/C++ 项目使用了默认设置。

对于 G++-Linker-Flags，他们做了一些在我看来非常奇怪的事情：他们打算链接 newlib-nano（即标准库的小版本）。

但是，通常您需要决定是否打算使用重定向并因此链接到 nosys.specs，这也会使您的二进制文件更大，或者是 nano.specs 的简约版本。

但是，他们确实列出了这两个选项，这对我来说没有意义。所以我检查了另一个项目设置（这是在 STM32 的 CM3 上），他们显然也是这样做的。这是为什么呢？

如果我不打算使用重定向（例如文件系统、printf/_write 等），我是否需要列出 nosys.specs？

其他问题：这些标志的顺序是否重要，或者这只是您要添加的所有选项的列表？

-g3 -gdwarf-2 -mcpu=cortex-m3 -mthumb -T "${BuildArtifactFileBaseName}.ld" --specs=nosys.specs -Xlinker --gc-sections -Xlinker -Map="${BuildArtifactFileBaseName}.map" --specs=nano.specs

Answer 1

但是，他们确实列出了这两个选项，这对我来说没有意义。

这很有意义。如果没有 nosys，您需要提供大量函数的定义或使用其他库，例如 semihostig。

简单例子：（main.c 就是 hello world 程序）

piotr@PiotrLaptop02:~$ arm-none-eabi-gcc --specs=nano.specs main.c
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-exit.o): in function `exit':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/stdlib/../../../../../newlib/libc/stdlib/exit.c:64: undefined reference to `_exit'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-sbrkr.o): in function `_sbrk_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/sbrkr.c:51: undefined reference to `_sbrk'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-writer.o): in function `_write_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/writer.c:49: undefined reference to `_write'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-closer.o): in function `_close_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/closer.c:47: undefined reference to `_close'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-fstatr.o): in function `_fstat_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/fstatr.c:55: undefined reference to `_fstat'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-isattyr.o): in function `_isatty_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/isattyr.c:52: undefined reference to `_isatty'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-lseekr.o): in function `_lseek_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/lseekr.c:49: undefined reference to `_lseek'
/usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/9.2.1/../../../arm-none-eabi/lib/libc_nano.a(lib_a-readr.o): in function `_read_r':
/build/newlib-CVVEyx/newlib-3.3.0/build_nano/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/readr.c:49: undefined reference to `_read'
collect2: error: ld returned 1 exit status
piotr@PiotrLaptop02:~$ arm-none-eabi-gcc --specs=nano.specs --specs=nosys.specs main.c
piotr@PiotrLaptop02:~$  

如您所见，没有 nosys 它不会链接。