Cortex-M3 (EFM32GG) - Newlib-Nano 的 ARM-GCC 鏈接器標志

Question

我分析了一個由 Simplicity Studio 生成的項目（Silicon Labs 為其微控制器的 Eclipse IDE 變體）。

我使用了基於 arm-none-eabi-gcc 工具鏈的 ASM/C/C++ 項目的默認設置。

對於 G++-Linker-Flags，他們做了一些在我看來非常奇怪的事情：他們打算鏈接 newlib-nano（所以是標准庫的小版本）。

但是，通常您需要決定是否打算使用重定向並因此鏈接到 nosys.specs，這也會使您的二進制文件更大，或者是最小的 nano.specs。

但是，他們確實列出了這兩個選項，這對我來說沒有意義。 所以我檢查了另一個項目設置（這是在 STM32 的 CM3 上），他們顯然也是這樣做的。 為什么是這樣？

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

附加問題：這些標志的順序是否重要，或者這只是您要添加的所有選項的列表？

-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，他們確實列出了這兩個選項，這對我來說沒有意義。

這很有道理。 如果沒有nosys您需要提供大量函數的定義或使用另一個庫，例如用於 semihostig。

簡單示例：（main.c 只是 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:~$  

如您所見，如果沒有 nosys，它將無法鏈接。