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C++26 + import std 无法通过 mcpp 构建 #99
Description
环境
- mcpp: 0.0.41
- 工具链: gcc@16.1.0 (xlings-fromsource)
- 系统: Fedora 44, x86_64
项目配置 (mcpp.toml)
[package]
name = "M3Lib"
version = "0.1.0"
[targets.M3Lib]
kind = "lib"
[lib]
path = "m3/m3.cppm"
[build]
sources = ["m3/**/*.cppm"]
cxxflags = ["-std=c++26", "-fcontracts"]
[toolchain]
default = "gcc@16.1.0"实际输出
$ mcpp build
Resolving toolchain
Resolved gcc@16.1.0 → @mcpp/registry/data/xpkgs/xim-x-gcc/16.1.0/bin/g++
Compiling M3Lib v0.1.0 (.)
error: build failed
In module imported at /home/skyler/Dev/M3Lib/m3/detail/alignment_traits.cppm:5:1:
std: error: language dialect differs 'C++23', expected 'C++26/contracts'
std: error: failed to read compiled module: Bad file data
std: note: compiled module file is 'gcm.cache/std.gcm'
std: fatal error: returning to the gate for a mechanical issue
compilation terminated.
In module imported at /home/skyler/Dev/M3Lib/m3/detail/concepts.cppm:7:1:
std: error: language dialect differs 'C++23', expected 'C++26/contracts'
std: error: failed to read compiled module: Bad file data
std: note: compiled module file is 'gcm.cache/std.gcm'
std: fatal error: returning to the gate for a mechanical issue
compilation terminated.
补充信息
GCC 16.x 在 -std=c++26 下隐式启用 contracts：
$ g++ -std=c++26 -E -dM -x c++ - < /dev/null | grep contract
#define __cpp_contracts 202502L-std=c++26 本身就会让方言变为 C++26/contracts，与 mcpp std 模块的 C++23 不匹配。
纯 C++23 项目（无 -std=c++26 和 -fcontracts）可以正常构建。
Activity
Sunrisepeak commentedon Jun 1, 2026
改功能已经支持, 使用
xlings update mcpp -y更新到最新版本(0.0.42)即可使用具体文档
https://github.com/mcpp-community/mcpp/blob/main/docs/05-mcpp-toml.md#23-build--%E6%9E%84%E5%BB%BA%E9%85%8D%E7%BD%AE
Sunrisepeak commentedon Jun 6, 2026
该问题已经解决, 如果还有问题可以reopen