我不能用arm-none-eabi-gcc编译

Question

我试图用arm-none-eabi-gcc编译代码，但我得到了以下错误。有没有人能帮我解释一下可能的原因？

谢谢!

/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-exit.o): In function `exit':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/stdlib/../../../../../newlib/libc/stdlib/exit.c:70: undefined reference to `_exit'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-fstatr.o): In function `_fstat_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/fstatr.c:62: undefined reference to `_fstat'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-openr.o): In function `_open_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/openr.c:59: undefined reference to `_open'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-sbrkr.o): In function `_sbrk_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/sbrkr.c:58: undefined reference to `_sbrk'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-writer.o): In function `_write_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/writer.c:58: undefined reference to `_write'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-closer.o): In function `_close_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/closer.c:53: undefined reference to `_close'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-isattyr.o): In function `_isatty_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/isattyr.c:58: undefined reference to `_isatty'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-lseekr.o): In function `_lseek_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/lseekr.c:58: undefined reference to `_lseek'
/usr/lib/gcc/arm-none-eabi/4.9.3/../../../arm-none-eabi/lib/libc.a(lib_a-readr.o): In function `_read_r':
/build/newlib-5zwpxE/newlib-2.2.0+git20150830.5a3d536/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/readr.c:58: undefined reference to `_read'

Answer 1

由于您是针对裸机目标进行编译的，因此在缺省情况下，newlib不会提供仅在具有控制台和硬盘驱动器的系统上才有意义的函数的实现，例如，基本上是诸如read/write/open/close/...之类的系统调用

如果你不需要这些函数，使用--specs=nosys.specs选项将使你的应用程序链接到默认的，基本上是空的实现，当调用时将返回一个错误代码：

/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/arm-none-eabi-gcc -o hello hello.c
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-exit.o): in function `exit':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/stdlib/exit.c:64: undefined reference to `_exit'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-sbrkr.o): in function `_sbrk_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/sbrkr.c:51: undefined reference to `_sbrk'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-writer.o): in function `_write_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/writer.c:49: undefined reference to `_write'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-closer.o): in function `_close_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/closer.c:47: undefined reference to `_close'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-lseekr.o): in function `_lseek_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/lseekr.c:49: undefined reference to `_lseek'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-readr.o): in function `_read_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/readr.c:49: undefined reference to `_read'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-fstatr.o): in function `_fstat_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/fstatr.c:55: undefined reference to `_fstat'
/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/lib/libc.a(lib_a-isattyr.o): in function `_isatty_r':
/tmp/dgboter/bbs/rhev-vm10--rhe6x86_64/buildbot/rhe6x86_64--arm-none-eabi/build/src/newlib-cygwin/newlib/libc/reent/isattyr.c:52: undefined reference to `_isatty'
$

使用--specs=nosys.specs选项：

/opt/arm/9/gcc-arm-9.2-2019.12-x86_64-arm-none-eabi/bin/arm-none-eabi-gcc --specs=nosys.specs -o hello hello.c 
$

如果您希望对那些缺少的系统调用进行自定义实现，另一种方法是从newlib libgloss/arm/syscalls.c源文件创建您自己的最小syscalls.c：您可以实现一些系统调用，然后清除其他不需要的系统调用。可以从here浏览newlib源代码，更多详细信息请参阅newlib documentation的12 System Calls和12.1 Definitions for OS interface一节。