// mcpp.fallback.probe_sysroot — sysroot detection strategies.

//

// Three strategies for discovering the sysroot:

// 1. Remap GCC's baked-in build-time sysroot to the local xpkgs layout

// 2. Parse Clang's .cfg file for --sysroot=

// 3. macOS: use xcrun to discover the SDK path

module;

#include <cstdlib>

export module mcpp.fallback.probe_sysroot;

import std;

import mcpp.xlings;

import mcpp.platform;

import mcpp.log;

export namespace mcpp::fallback {

// When GCC reports a sysroot ending in "subos/default" that doesn't exist

// on the current machine (baked build-time path), remap it to the

// equivalent sysroot relative to the compiler's own xpkgs directory.

std::optional<std::filesystem::path>

remap_xlings_baked_sysroot(std::string_view reportedPath,

const std::filesystem::path& compilerBin) {

if (reportedPath.empty()) return std::nullopt;

if (!reportedPath.ends_with("subos/default")) return std::nullopt;

if (std::filesystem::exists(std::string(reportedPath))) return std::nullopt;

if (auto xpkgs = mcpp::xlings::paths::xpkgs_from_compiler(compilerBin)) {

// xpkgs is <registry>/data/xpkgs -> registry = xpkgs/../..

auto registrySysroot = xpkgs->parent_path().parent_path()

/ "subos" / "default";

if (std::filesystem::exists(registrySysroot / "usr" / "include"))

return registrySysroot;

}

return std::nullopt;

}

// Parse a Clang .cfg file alongside the compiler binary for --sysroot=.

std::optional<std::filesystem::path>

parse_clang_cfg_sysroot(const std::filesystem::path& compilerBin) {

auto stem = compilerBin.stem().string();

auto cfgPath = compilerBin.parent_path() / (stem + ".cfg");

if (!std::filesystem::exists(cfgPath)) return std::nullopt;

std::ifstream ifs(cfgPath);

std::string line;

while (std::getline(ifs, line)) {

constexpr std::string_view prefix = "--sysroot=";

if (line.starts_with(prefix)) {

// Trim whitespace

auto val = std::string(line.substr(prefix.size()));

while (!val.empty() && (val.back() == '\n' || val.back() == '\r' || val.back() == ' '))

val.pop_back();

while (!val.empty() && (val.front() == '\n' || val.front() == '\r' || val.front() == ' '))

val.erase(val.begin());

if (!val.empty() && std::filesystem::exists(val))

return std::filesystem::path(val);

}

}

return std::nullopt;

}

// macOS fallback: use xcrun to discover the SDK path.

std::optional<std::filesystem::path>

probe_macos_sdk_sysroot() {

auto sdk = mcpp::platform::macos::sdk_path();

if (sdk) {

mcpp::log::verbose("probe", std::format("sysroot (macOS SDK): {}", sdk->string()));

}

return sdk;

}

} // namespace mcpp::fallback