ARM GCC 11.3 Rel1 newlib-nano linker warning _read is not implemented and will always fail

Hi! Upgrading to ARM GCC 11.3 from 7.3 and noticed these linker warnings on  bare metal embedded project. These linker warnings aren't on 7.3 or 11.2 ARM GCC versions. I'm having a tough time understanding why they are happening on ARM GCC 11.3 now.


Using the linker spec files:
nosys.specs
nano.specs

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-closer.o): in function `_close_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/closer.c:47: warning: _close is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-fstatr.o): in function `_fstat_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/fstatr.c:55: warning: _fstat is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-isattyr.o): in function `_isatty_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/isattyr.c:52: warning: _isatty is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-signalr.o): in function `_kill_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/signalr.c:53: warning: _kill is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-lseekr.o): in function `_lseek_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/lseekr.c:49: warning: _lseek is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-openr.o): in function `_open_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/openr.c:50: warning: _open is not implemented and will always fail

arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(libc_a-readr.o): in function `_read_r':

/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/readr.c:49: warning: _read is not implemented and will always fail

Parents
  • I was in the same situation (got these warnings after upgrading projects toolchain to ARM GCC v11.3.rel1), precisely:

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-closer.o): in function `_close_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/closer.c:47: warning: _close is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-lseekr.o): in function `_lseek_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/lseekr.c:49: warning: _lseek is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-readr.o): in function `_read_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/readr.c:49: warning: _read is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-writer.o): in function `_write_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/writer.c:49: warning: _write is not implemented and will always fail

    I confirmed that the functions that the linker compained about were not even emitted in the generated ELF file (NO symbols containing "read", "lseek", "open").

    But for me, changing the linker specs from --specs=nosys.specs (which used to work flawlesssly with older GCC versions) to --specs=nano.specs fixed all these warnings, requiring no further changes (I did NOT provide function definitions for _write, _read, _lseek or similar)

    Additional compiler flags I used: -Wall -Wextra -ffunction-sections -fdata-sections

    Linker flags I used:  -Wl,--gc-sections

    TL;DR:

    Just switching linker specs from --specs=nosys.specs to --specs=nano.specs might fix this for you!

Reply
  • I was in the same situation (got these warnings after upgrading projects toolchain to ARM GCC v11.3.rel1), precisely:

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-closer.o): in function `_close_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/closer.c:47: warning: _close is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-lseekr.o): in function `_lseek_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/lseekr.c:49: warning: _lseek is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-readr.o): in function `_read_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/readr.c:49: warning: _read is not implemented and will always fail

    /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /opt/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-writer.o): in function `_write_r':

    /data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/writer.c:49: warning: _write is not implemented and will always fail

    I confirmed that the functions that the linker compained about were not even emitted in the generated ELF file (NO symbols containing "read", "lseek", "open").

    But for me, changing the linker specs from --specs=nosys.specs (which used to work flawlesssly with older GCC versions) to --specs=nano.specs fixed all these warnings, requiring no further changes (I did NOT provide function definitions for _write, _read, _lseek or similar)

    Additional compiler flags I used: -Wall -Wextra -ffunction-sections -fdata-sections

    Linker flags I used:  -Wl,--gc-sections

    TL;DR:

    Just switching linker specs from --specs=nosys.specs to --specs=nano.specs might fix this for you!

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