i can't compile with arm-none-eabi-gcc

Question

I am trying to compile code with arm-none-eabi-gcc, but I get the following errors. Can someone help me or explain to me what is the possible reason?

Thank you!

/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

Because you are compiling for a bare-metal target, newlib does not by default provide implementations for the functions that make only sense on a system with a console and an hard drive for example, basically system calls such as read/write/open/close/...

If you don' t need to those functions, using the --specs=nosys.specs option will make your application link with default, basically empty implementations that will return an error code when called:

/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'
$

Using the --specs=nosys.specs option:

/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 
$

An alternative, if you want to have your custom implementation of those missing system calls, is to create your own, minimal syscalls.c from the newlib libgloss/arm/syscalls.c source file: you can implement some system calls, and stubbing the others you don't need. newlib source code can be browsed from here, and see section 12 System Calls and 12.1 Definitions for OS interface of the newlib documentation for more details.