什么是“nosys"、“nano"、“rdimon"?使用 ARM GCC 时的术语? [英] What are "nosys", "nano", "rdimon" terms when using ARM GCC?
问题描述
我正在学习使用 GCC 工具链编写 ARM 代码.我遇到了一些找不到文档的 GCC 选项.有人可以帮忙解释一下他们是做什么的吗?
I am learning to write ARM code using the GCC toolchain. I've run into a few GCC options that I cannot find documentation for. Could someone please help explain what they do?
-specs=nosys.specs-specs=nano.specs-specs=rdimon.specs-lnosys
-specs=nosys.specs 和 -lnosys 有什么关系?你是一起使用它们，还是它们相互排斥，或者其他什么?
How do -specs=nosys.specs and -lnosys relate? Do you use them together, or are they exclusive of each other, or something else?
还有nano，我收集到暗示使用newlib-nano 库.我已经看到它与 -lm 和 -lc 结合使用.这只是给你标准的 libc 和 libm 函数吗?
And nano, I've gathered to imply using the newlib-nano library. I've seen this used in conjunction with -lm and -lc. Does this just give you the standard libc and libm functions?
rdimon 代表什么?我知道这是用于半主机"，这意味着以某种方式使用主机 IO.这是否意味着我可以打印到主机控制台?我找不到有关如何实际使用它的文档.
What does rdimon stand for? I understand it is for "semihosting", which means using the host IO somehow. Does this mean I can printf to the host console? I can find no documentation on how to actually use this.
如果我在某处找不到所有这些的真实来源，请告诉我.
If there is a source of truth for all of this somewhere that I haven't found, please let me know.
感谢您帮助澄清.
推荐答案
Gcc 使用 specs-strings，它控制要运行的子进程以及它应该传递给它们的参数.spec-strings 定义的行为可以使用 spec-files 覆盖，其目的和语法记录在此处:https://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html
Gcc uses specs-strings, which control which subprocesses to run and what parameters it shall pass to them. The behavior defined by the spec-strings can be overridden using spec-files, whose purpose and syntax is documented here: https://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html
查看gcc工具链的lib文件夹中的这些spec文件(例如/usr/lib/arm-none-eabi/lib)我们可以看到提到的spec文件定义了哪个标准库将由链接器使用.
Looking at these spec files in the lib folder of the gcc tool chain (e.g. /usr/lib/arm-none-eabi/lib) we can see that the mentioned spec files define which standard library is to be used by the linker.
例如，nosys.specs 只是定义系统调用应该被实现为调用时返回错误的存根 (-lnosys).在这种情况下，libc 的选择取决于是否应该使用 nano.使用 %G 处理 libgcc spec-string，它定义了传递给链接器的参数.
For example, nosys.specs just defines that system calls should be implemented as stubs that return errors when called (-lnosys). The choice of libc in this case depends on whether nano should be used. With %G the libgcc spec-string is processed, which defines the parameters passed to the linker.
nosys.specs:
nosys.specs:
%rename link_gcc_c_sequence nosys_link_gcc_c_sequence
*nosys_libgloss:
-lnosys
*nosys_libc:
%{!specs=nano.specs:-lc} %{specs=nano.specs:-lc_nano}
*link_gcc_c_sequence:
%(nosys_link_gcc_c_sequence) --start-group %G %(nosys_libc) %(nosys_libgloss) --end-group
nano.specs 定义了使用 newlib-nano 的系统包含路径和库参数.规范文件包含替换 -lc 和其他 nano 等价物，例如-lc_nano.因此，将它与这些结合使用将使 gcc 仍然将 nano 库传递给链接器.
nano.specs defines the system include path and library parameters to use newlib-nano. The spec file contains replacements for -lc and others to nano equivalents, e.g. -lc_nano. So using it in conjunction with these will make gcc still pass nano libaries to the linker.
使用rdimon.specs，-lrdimon 作为标准库的libgloss 部分传递.这基本上意味着您可以使用系统调用(也可以使用 printf)，但这依赖于附加的调试器，如果没有调试器，CPU 可能会崩溃.
Using rdimon.specs, -lrdimon is passed as the libgloss part of the standard library. This basically means that you can use system calls (and also printf), but this relies on a debugger being attached, and the CPU may crash if no debugger is present.
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