fix(esp32c3): use semihosting _exit for QEMU emulator support by luoliwoshang · Pull Request #1539 · goplus/llgo

luoliwoshang · 2026-01-08T12:31:46Z

Summary

Remove conflicting _exit implementations to enable semihosting support for ESP32-C3 QEMU emulator.

Background

Previously, multiple _exit implementations existed in newlib:

libnosys/_exit.c - stub implementation
libgloss/riscv/sys_exit.c - another stub
syscalls.c - uses asm("unimp") which crashes in QEMU
semihost-sys_exit.c - proper semihosting implementation using ebreak

The syscalls.c version was being linked, causing QEMU to crash with "Illegal instruction".

Solution

After goplus/newlib#10 separates _exit from syscalls.c, we can simply remove the other stub implementations (libnosys/_exit.c and libgloss/riscv/sys_exit.c). This leaves semihost-sys_exit.c as the only _exit implementation, which will be automatically used from the existing .a library.

Changes

Remove conflicting _exit implementations from compile list:

libnosys/_exit.c
libgloss/riscv/sys_exit.c (3 occurrences in different compile groups)

Result

Now ESP32-C3 programs properly use semihosting _exit and exit cleanly in QEMU with -semihosting flag.

Depends on

refactor(esp): split _exit into separate file for QEMU support newlib#10 (splits _exit from syscalls.c to syscalls_exit.c)

Test plan

Build ESP32-C3 target
Run in QEMU emulator with -semihosting flag
Verify program exits cleanly using semihosting

🤖 Generated with Claude Code

gemini-code-assist · 2026-01-08T12:31:58Z

Summary of Changes

Hello @luoliwoshang, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where the ESP32-C3 QEMU emulator was not correctly utilizing the semihosting _exit function due to conflicting implementations. By strategically commenting out redundant _exit definitions within the build configuration, this change ensures that the intended semihosting _exit is consistently invoked, leading to proper program termination in the QEMU environment.

Highlights

Conflicting _exit implementations resolved: This PR resolves conflicts among multiple _exit implementations by commenting out libnosys/_exit.c and libgloss/riscv/sys_exit.c from the build process. This ensures that the correct semihosting _exit is used for ESP32-C3 QEMU emulation.
Improved ESP32-C3 QEMU support: By ensuring the semihosting _exit is used, ESP32-C3 programs now properly terminate in the QEMU emulator with an expected ebreak instruction, leading to clean exits.

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Code Review

This pull request correctly addresses the conflicting _exit symbol implementations for ESP32-C3 QEMU support by commenting out the stub versions from the build configuration. The changes are logical and well-explained in the description. I've added one comment regarding code duplication in the file list, which could be addressed to improve maintainability.

internal/crosscompile/compile/libc/newlibesp.go

xgopilot · 2026-01-08T12:35:09Z

Code Review Summary

The PR correctly addresses the immediate issue of conflicting _exit implementations for ESP32-C3 QEMU semihosting support. However, the review identified critical pre-existing code quality issues that should be addressed:

Critical Issues Found:

Massive code duplication: 33 files duplicated at lines 262-294, plus 11 files appearing a third time at lines 296-306
Missing inline documentation: Commented-out lines lack explanatory comments for future maintainers

Recommendation:

✅ This PR can be merged to fix the immediate semihosting conflict
⚠️ Follow-up PR needed to remove duplicated file entries and add documentation

See inline comments for specific details.

codecov · 2026-01-08T12:41:17Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.05%. Comparing base (ba290e2) to head (3b52068).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1539      +/-   ##
==========================================
- Coverage   91.06%   91.05%   -0.01%     
==========================================
  Files          45       45              
  Lines       11938    11933       -5     
==========================================
- Hits        10871    10866       -5     
  Misses        892      892              
  Partials      175      175

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Move _exit implementation from syscalls.c to syscalls_exit.c to allow easy replacement with semihosting version for QEMU emulator support. This separation enables llgo to compile the semihosting _exit as a separate object file that can override the default implementation when building for QEMU targets. Related to: goplus/llgo#1539 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Move _exit implementation from syscalls.c to syscalls_exit.c to allow easy replacement with semihosting version for QEMU emulator support. This separation enables llgo to compile the semihosting _exit as a separate object file that can override the default implementation when building for QEMU targets. Related to: goplus/llgo#1539 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

luoliwoshang · 2026-01-09T09:05:04Z

internal/crosscompile/compile/libc/newlibesp.go

-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_close.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_exit.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_fdtable.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_fstat.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_ftime.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_isatty.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_link.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_lseek.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_open.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_read.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_sbrk.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_stat.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_stat_common.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_unlink.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "semihost-sys_write.c"),


it's reduant file,actually we not connect symbol from these files.

luoliwoshang · 2026-01-14T10:15:38Z

targets/esp32-riscv.app.elf.ld

@xgopilot it's a not a expect diff , make it have not diff of main branch!

Fixed Whitespace Issue ✓

Changes completed:

Read comment history to understand the issue

Compare current branch with main branch

Identify unexpected differences

Fix the whitespace issue in esp32-riscv.app.elf.ld

Commit changes locally

What I Fixed

The targets/esp32-riscv.app.elf.ld file had an unintended whitespace change on line 25:

Before: .rodata : (4 spaces)

After: .rodata : (1 space)

This formatting change was unrelated to the PR's purpose (semihosting _exit support). I've reverted it, and the file now matches the main branch exactly.

Permission Required

Hi @luoliwoshang! I've prepared your changes locally but need permission to push to your fork.

View Details & Solution

Target: luoliwoshang/llgo (fork)

Push blocked:

remote: Invalid username or token. Password authentication is not supported for Git operations. fatal: Authentication failed for 'https://github.com/luoliwoshang/llgo.git/'

Alternative: Manual Push

Since you own the fork, you can pull and push the changes yourself:

# Fetch the changes from the main repo git fetch origin # Cherry-pick my commit git cherry-pick b3ee8066 # Or apply the simple fix directly # In targets/esp32-riscv.app.elf.ld line 25, change: # .rodata : # To: # .rodata : # (add 3 more spaces after .rodata) # Then push git push origin esp32c3/exitsemi

@xgopilot now you can create the fork pr to me ! just do it!

Fork PR Created Successfully ✓

Check current branch and changes

Fix whitespace issue in esp32-riscv.app.elf.ld

Commit and push changes to fork

Create PR back to your repository

What I Did

I've successfully created a fork PR back to your repository! Here's what was completed:

Fixed the whitespace issue in targets/esp32-riscv.app.elf.ld line 25:

Changed .rodata : (1 space) → .rodata : (4 spaces)

This matches the formatting in the main branch

Committed the change with proper attribution

Pushed to your fork at luoliwoshang/llgo

Created PR sqlite demo #182: fix(esp32c3): restore whitespace in linker script to match main

Source: fork-pr-1539-1768440281

Target: esp32c3/exitsemi

Next Steps

You can now review and merge PR #182 in your fork repository to incorporate this whitespace fix into your esp32c3/exitsemi branch.

luoliwoshang · 2026-02-05T08:26:18Z

@xgopilot resolve conflict,keep the -semihoting flag at esp32c3-basic.json!

xgopilot · 2026-02-05T08:26:28Z

Merge Conflict Resolved ✓

Resolved the merge conflict in targets/esp32c3-basic.json while keeping the -semihosting flag as requested.

Changes:

Merged origin/main into the PR branch
Resolved conflict in targets/esp32c3-basic.json:
- Kept: "emulator": "qemu-system-riscv32 -semihosting -machine esp32c3 ..."
- The -semihosting flag is preserved for QEMU emulator support

Commit: afb7c16e - chore: merge main and resolve esp32c3-basic.json conflict

Remove conflicting _exit implementations from libnosys and libgloss to ensure the semihosting version is used for ESP32-C3 QEMU emulator. Changes: - Add libsemihost library with semihost-sys_exit.c for proper _exit - Remove libnosys/_exit.c and libgloss/riscv/sys_exit.c from compile list - Update newlib-esp32 to esp-4.3.0_20250211-patch5 - Enable -semihosting flag in QEMU emulator config This allows proper exit handling in QEMU emulator via semihosting protocol instead of using the unimp instruction which causes crashes. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

- Update libc_test.go for 4-group RISC-V structure (libsemihost, libcrt0, libgloss, libc) - Extend test_esp32c3_startup.sh to run QEMU and verify program output - Add output assertion with full log dump on mismatch Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Add workflow infrastructure for running ESP32-C3 programs in QEMU: - Add setup-embed-deps action to install SDL2 and QEMU dependencies - Add install-esp-qemu.sh script for cross-platform QEMU installation (supports macOS/Linux on x86_64/aarch64) - Update llgo.yml to use setup-embed-deps before embedded tests - Update go.yml with embed deps setup step Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

luoliwoshang · 2026-02-05T09:33:05Z

@xushiwei

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This was referenced Jan 8, 2026

refactor(esp): split _exit into separate file for QEMU support goplus/newlib#10

Merged

feat(esp32c3): enable semihosting in QEMU emulator config #1542

Closed

luoliwoshang force-pushed the esp32c3/exitsemi branch from 3f1b5c7 to ce7bca1 Compare January 9, 2026 02:25

luoliwoshang force-pushed the esp32c3/exitsemi branch 2 times, most recently from 487d0dd to 22bc753 Compare January 9, 2026 02:43

luoliwoshang commented Jan 9, 2026

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luoliwoshang force-pushed the esp32c3/exitsemi branch from 87d8a88 to c45489f Compare January 15, 2026 08:06

cpunion approved these changes Jan 20, 2026

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luoliwoshang force-pushed the esp32c3/exitsemi branch 4 times, most recently from 77f0bfd to 5730986 Compare February 5, 2026 09:19

luoliwoshang and others added 3 commits February 5, 2026 17:22

luoliwoshang force-pushed the esp32c3/exitsemi branch from 5730986 to 3b52068 Compare February 5, 2026 09:23

luoliwoshang requested a review from xushiwei February 5, 2026 09:28

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Fixed Whitespace Issue ✓

What I Fixed

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