debug: revert to simple _putenv_s + add diagnostic output on build failure

Author: Sunrisepeak

.github/workflows/ci-windows.yml

@@ -75,7 +75,16 @@ jobs:
         run: |
           export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
 
-          "$MCPP" build
+          "$MCPP" build || {
+            echo "=== Debug: mcpp sandbox ==="
+            find "$USERPROFILE/.mcpp" -name "*.exe" -o -name "xpkgs" -type d 2>/dev/null | head -20
+            echo "=== Debug: xlings home ==="
+            find "$USERPROFILE/.xlings" -path "*/xim-x-llvm*" -type d 2>/dev/null | head -10
+            echo "=== Debug: mcpp registry data ==="
+            ls -la "$USERPROFILE/.mcpp/registry/data/" 2>/dev/null || echo "no data dir"
+            ls -la "$USERPROFILE/.mcpp/registry/data/xpkgs/" 2>/dev/null || echo "no xpkgs dir"
+            exit 1
+          }
 
           MCPP_SELF=$(find target -name "mcpp.exe" -path "*/bin/*" | head -1)
           test -n "$MCPP_SELF" || { echo "FAIL: no mcpp.exe"; exit 1; }

src/xlings.cppm

@@ -428,18 +428,14 @@ std::filesystem::path sandbox_init_marker(const Env& env) {
 std::string build_command_prefix(const Env& env) {
     auto xvmBin = paths::sandbox_bin(env).string();
 #if defined(_WIN32)
-    // Windows: set environment variables via _putenv_s (inherited by
-    // child processes) AND cd to the sandbox home (xlings may use cwd
-    // to resolve its home). Return a "cd /d <home> && <binary>" prefix.
     _putenv_s("XLINGS_HOME", env.home.string().c_str());
     _putenv_s("XLINGS_PROJECT_DIR",
               env.projectDir.empty() ? "" : env.projectDir.string().c_str());
     {
         std::string newPath = xvmBin + ";" + (std::getenv("PATH") ? std::getenv("PATH") : "");
         _putenv_s("PATH", newPath.c_str());
     }
-    return std::format("cd /d \"{}\" && \"{}\"",
-        env.home.string(), env.binary.string());
+    return env.binary.string();
 #else
     if (env.projectDir.empty()) {
         // Global mode: unset XLINGS_PROJECT_DIR (existing behavior).
@@ -663,15 +659,13 @@ int install_with_progress(const Env& env, std::string_view target,
         R"({{"targets":["{}"],"yes":true}})", target);
 
 #if defined(_WIN32)
-    // Ensure xlings sees XLINGS_HOME + runs from the sandbox dir.
-    // Both _putenv_s (inherited by child) and cd /d (working dir) are
-    // needed — xlings may resolve its home from either.
     _putenv_s("XLINGS_HOME", env.home.string().c_str());
     _putenv_s("XLINGS_PROJECT_DIR", "");
     std::error_code ec_mkdir;
     std::filesystem::create_directories(env.home, ec_mkdir);
-    auto cmd = std::format("cd /d \"{}\" && \"{}\" interface install_packages --args {} 2>nul",
-        env.home.string(),
+    // Use raw command — _putenv_s is inherited by popen child.
+    // No 2>nul — let xlings output be visible for debugging.
+    auto cmd = std::format("{} interface install_packages --args {}",
         env.binary.string(),
         shq(argsJson));
 #else
@@ -805,8 +799,7 @@ void ensure_init(const Env& env, bool quiet) {
 #if defined(_WIN32)
     _putenv_s("XLINGS_HOME", env.home.string().c_str());
     _putenv_s("XLINGS_PROJECT_DIR", "");
-    auto cmd = std::format("cd /d \"{}\" && \"{}\" self init",
-        env.home.string(), env.binary.string());
+    auto cmd = env.binary.string() + " self init";
 #else
     auto cmd = std::format(
         "cd {} && env -u XLINGS_PROJECT_DIR XLINGS_HOME={} {} self init >/dev/null 2>&1",