libcxxabi: Optimize cxx code size.

[cuiziwei1]

Summary

enable LIBSUPCXX:
text data bss dec hex filename
93080 592 5472 99144 18348 nuttx/nuttx

enable LIBCXXABI:
before:
text data bss dec hex filename
126468 352 5960 132780 206ac nuttx/nuttx

after:
text data bss dec hex filename
68048 352 5960 74360 12278 nuttx/nuttx

Impact

Testing

[nuttxpr]

[Experimental Bot, please feedback here]

Let's break down whether this Pull Request (PR) description meets the NuttX requirements.

Areas Where the PR Description is Lacking:

• Summary:
  • Why is this change necessary? Is it fixing a bug, adding a feature, or improving performance? The description only states "enable LIBSUPCXX" and "enable LIBCXXABI" without explaining the motivation.
  • What functional part of the code is changed? Be specific. What files or modules are affected by enabling these libraries?
  • How does the change work? Provide a technical explanation of how enabling these libraries impacts the NuttX build or runtime.
• Impact:
  • Almost all sections are blank. You must address each impact area. For enabled libraries, consider:
    • New feature: Does this unlock new C++ capabilities?
    • Build: How does enabling these libraries affect the build process, dependencies, or configuration?
    • Hardware: Are there any architecture-specific implications?
    • Compatibility: Does this affect compatibility with existing NuttX codebases or applications?
    • Security: Do these libraries introduce any potential security concerns?
• Testing:
  • Insufficient Detail:
    • Build Hosts: Specify the operating systems, architectures, and compilers used for testing.
    • Targets: List the specific architectures, boards, and configurations tested on.
  • Missing Logs: The "Testing logs before change" and "Testing logs after change" sections are empty. Provide actual log snippets demonstrating the change's effect.

How to Improve the PR Description:

1. Motivation: Clearly explain the reason for enabling LIBSUPCXX and LIBCXXABI. What benefits do they provide? What problem are you solving?

2. Technical Details:

   • Describe the specific code changes (files modified, configuration options, etc.).
   • Explain how enabling these libraries affects NuttX internally (memory usage, dependencies, etc.).

3. Complete the Impact Section:

   • Carefully analyze and document the impact on every aspect listed in the NuttX requirements.
   • Don't just say "NO" – provide justification. For example, "Impact on hardware: NO. These libraries are standard C++ components and do not introduce hardware-specific changes."

4. Provide Detailed Testing Information:

   • List the exact build hosts and target environments used for testing.
   • Include relevant snippets from your testing logs to demonstrate the before-and-after behavior.

Example of an Improved Summary:

This PR enables the LIBSUPCXX and LIBCXXABI libraries in the NuttX build system to provide support for essential C++ features, including exception handling and runtime type information (RTTI). These libraries are required for applications using modern C++ techniques and are commonly found in standard C++ environments. The change involves modifying the NuttX configuration system to include these libraries during the build process.

By following these recommendations, you'll create a much stronger PR that is more likely to be accepted. Remember, a good PR description is clear, comprehensive, and convincing!

[pkarashchenko]

====================================================================================
Configuration/Tool: esp32c3-devkit/cxx
2024-09-29 07:10:38
------------------------------------------------------------------------------------
  Cleaning...
  Configuring...
  Building NuttX...
riscv-none-elf-ld: warning: /Users/runner/work/nuttx/nuttx/sources/nuttx/nuttx has a LOAD segment with RWX permissions
riscv-none-elf-ld: /Users/runner/work/nuttx/nuttx/sources/nuttx/staging/libxx.a(exception.o): in function `std::uncaught_exception()':
exception.cpp:(.text._ZSt18uncaught_exceptionv+0x4): undefined reference to `__cxa_uncaught_exceptions'
make[1]: *** [nuttx] Error 1
make: *** [nuttx] Error 2

[cuiziwei1]

====================================================================================
Configuration/Tool: esp32c3-devkit/cxx
2024-09-29 07:10:38
------------------------------------------------------------------------------------
  Cleaning...
  Configuring...
  Building NuttX...
riscv-none-elf-ld: warning: /Users/runner/work/nuttx/nuttx/sources/nuttx/nuttx has a LOAD segment with RWX permissions
riscv-none-elf-ld: /Users/runner/work/nuttx/nuttx/sources/nuttx/staging/libxx.a(exception.o): in function `std::uncaught_exception()':
exception.cpp:(.text._ZSt18uncaught_exceptionv+0x4): undefined reference to `__cxa_uncaught_exceptions'
make[1]: *** [nuttx] Error 1
make: *** [nuttx] Error 2

[cuiziwei1]

This is my fault. A fix patch has been submitted. Please try compiling again.

[pkarashchenko]

The CI error now is

: && /tools/ccache/bin/c++  -Wl,--gc-sections -T nuttx.ld CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hostirq.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hostmemory.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hostmisc.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hosttime.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hostuart.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_tapdev.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hosthcisocket.c.o CMakeFiles/nuttx.dir/arch/sim/src/sim/posix/sim_hostfs.c.o CMakeFiles/nuttx.dir/empty.cxx.o -o nuttx  nuttx.rel  -lpthread  -lz  -lrt && :
/usr/bin/ld: nuttx.rel: in function `std::uncaught_exceptions()':
/github/workspace/sources/nuttx/libs/libxx/libcxx/src/support/runtime/exception_libcxxabi.ipp:21: undefined reference to `__cxa_uncaught_exceptions'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
cp: cannot stat 'nuttx': No such file or directory
HEAD detached at pull/13721/merge
Untracked files:
  (use "git add <file>..." to include in what will be committed)
	libs/libxx/libcxx.rej

[xiaoxiang781216]

@cuiziwei1 please fix the ci error.