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

Question

我分析了Silicon (面向微控制器的Silicon Labs的Eclipse IDE变体)生成的一个项目。

我使用了一个基于arm-none-eabi-gcc工具链的ASM/C/C++项目的默认设置。

对于G++-Linker-Flags，他们做了一些对我来说非常奇怪的事情:他们打算链接到newlib-nano (所以是标准库的小版本)。

然而，通常你需要决定你是否打算使用重定向，从而链接到nosys.specs，这也会使你的二进制文件更大，或者是最简单的nano.specs。

然而，他们确实列出了两个选项，这对我来说是没有意义的。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。为什么会这样呢？

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

附加问题:这些标志的顺序重要吗?或者这只是您想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

然而，他们确实列出了两个选项，这对我来说是没有意义的。

这很有意义。在没有nosys的情况下，您需要提供大量函数的定义，或者使用其他库，例如用于半主机。

简单的例子：(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:~$  

如你所见，如果没有nosys，它将无法链接。