gcc-arm-none-eabi 11.3“没有实施，永远失败”

Question

我正在做一个裸金属STM32项目，在Linux x64主机上编译。

在将我的工具链从gcc-arm-none-eabi-11.2-2022.02升级到arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi之后，我会得到以下链接器警告：

warning: _close is not implemented and will always fail
warning: _fstat is not implemented and will always fail
warning: _getpid is not implemented and will always fail
warning: _isatty is not implemented and will always fail
warning: _kill is not implemented and will always fail
warning: _lseek is not implemented and will always fail
warning: _open is not implemented and will always fail
warning: _read is not implemented and will always fail
warning: _write is not implemented and will always fail

更全面地说，我明白了：

~/dev_tools/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: ~/dev_tools/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.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
~/dev_tools/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: ~/dev_tools/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/libc.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
~/dev_tools/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: ~/dev_tools/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/libc.a(libc_a-signalr.o): in function `_getpid_r':
/data/jenkins/workspace/GNU-toolchain/arm-11/src/newlib-cygwin/newlib/libc/reent/signalr.c:83: warning: _getpid is not implemented and will always fail
~/dev_tools/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: ~/dev_tools/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/libc.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
~/dev_tools/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: ~/dev_tools/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/libc.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
~/dev_tools/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: ~/dev_tools/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.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
~/dev_tools/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: ~/dev_tools/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/libc.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
~/dev_tools/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: ~/dev_tools/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.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
~/dev_tools/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: ~/dev_tools/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.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

除此之外，这个项目似乎编译得很好。在阅读发布说明(可在这里找到)时，我看不出是什么原因造成的。

1. 是什么改变导致了这一切？
2. 我可以无视这些警告吗？看上去像是系统呼叫，所以我想我可以？
3. 如果是的话，他们会不会被压制？

Answer 1

与gcc-arm-none-eabi一起提供的库称为'newlib‘。您可以从git://newlib eware.org/git/newlib-cygwin.git下载一个副本。它有标记，您可以确定编译器发布的特定版本，并获得标记版本。

例如，syscalls.c是一个实现。Libc存根文档包含要实现的函数。但是，您可能会想知道为什么会收到这些警告。有各种'C‘库函数调用，如srand()、assert()等，而将拖入'C’文件库。如果您希望最小化开销，则需要查看映射文件并避免这些函数调用。

我不确定你的代码库和地图文件的子部分将是有帮助的。给你，

• _open_r
• _close_r
• _read_r

来自“reent”的可再入图书馆。通常，可重入的功能只适用于实时操作系统或桌面操作系统.如果你有一个裸露的金属单主螺纹，你不需要这些功能。您不能使用以下选项在中断处理程序中调用open() :)因此，实际上只有一个上下文(以及一个errno )。‘可重入者’的功能是无用的。与.fini部分一样，嵌入式设备通常不会“关机”，它们会重新启动。

是什么改变导致了这一切？

您已经链接到了在'C‘库中引入文件系统原语的东西(称为函数)。

我可以无视这些警告吗？

这取决于您的用例。你是一个安全关键系统吗？一般来说，我建议修复它们，这样下一个人就不会感到困惑了。最有可能的情况是，如果代码遵循这些函数的路径，那么某些东西已经出错/无法处理。

看上去像是系统呼叫，所以我想我可以？

不是问题？

如果是的话，他们会不会被压制？

要么避免函数，要么提供“做正确的事情”的替代实现。“正确的事情”将取决于你的平台。

Answer 2

这些是系统调用需要实现的方法，您使用了标准库(NEWLIB)的功能，所以如果您确定不需要实现这些方法，则应该根据您自己的平台实现这些方法，只需在链接add链接中添加一个空的实现即可

void _close(void)
{
}
void _lseek(void)
{

}
void _read(void)
{
}
void _write(void)
{
}

在此之前

[ 50%] Building C object CMakeFiles/xpad.dir/src/main.c.o
[100%] Linking C executable xpad
/home/wangkai/workspace/xpad/toolchain/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: /home/wangkai/workspace/xpad/toolchain/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/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
/home/wangkai/workspace/xpad/toolchain/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: /home/wangkai/workspace/xpad/toolchain/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/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
/home/wangkai/workspace/xpad/toolchain/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: /home/wangkai/workspace/xpad/toolchain/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/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
/home/wangkai/workspace/xpad/toolchain/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: /home/wangkai/workspace/xpad/toolchain/arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/lib/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
[100%] Built target xpad

之后

[ 33%] Building C object CMakeFiles/xpad.dir/src/system_call.c.o
[ 66%] Linking C executable xpad
[100%] Built target xpad