我正在尝试使用arm-none-eabi-gcc编译代码，但是出现以下错误。有人可以帮助我或向我解释可能的原因是什么？
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'
答案 0 :(得分：2)
由于要为裸机目标进行编译，因此newlib默认情况下不提供仅在具有控制台和硬盘驱动器的系统上有意义的功能的实现，基本上是诸如read / write / open / close / ...
如果不需要这些功能，则使用--specs=nosys.specs选项将使您的应用程序具有默认的链接，基本上是空的实现，在调用时将返回错误代码：
/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
$
如果要对丢失的系统调用进行自定义实现，则可以从syscalls.c newlib源文件创建自己的最小libgloss/arm/syscalls.c：一些系统调用，并存根其他不需要的系统调用。
可以从here浏览newlib源代码，有关更多详细信息，请参见12 System Calls documentation的12.1 Definitions for OS interface和newlib部分。