fix: rpath only dependency runtime dirs; update first-run default test

R2 precision: baking ALL of plan.runtimeLibraryDirs into -L/-rpath pulled the
glibc payload dir into musl/static links (undefined _DYNAMIC; broke e2e 28/30).
Split out plan.depRuntimeLibraryDirs (dependency [runtime] library_dirs only,
e.g. compat.glx-runtime) and emit toolchain.linkRuntimeDirs + dep dirs, as
before plus the dep closure. e2e 29 updated for the intentional glibc
first-run default (musl-static is opt-in via --target).

Author: d2learn-org

src/build/flags.cppm

@@ -262,13 +262,16 @@ CompileFlags compute_flags(const BuildPlan& plan) {
     std::string static_stdlib = (f.staticStdlib && !isClang && !mcpp::platform::is_windows) ? " -static-libstdc++" : "";
     std::string runtime_dirs;
     if constexpr (mcpp::platform::supports_rpath) {
-        // Bake ALL resolved runtime library dirs into the binary's RUNPATH —
-        // not just the toolchain's. plan.runtimeLibraryDirs is the union of
-        // dependency packages' [runtime] library_dirs (e.g. compat.glx-runtime's
-        // host-GL passthrough dir) plus the toolchain/payload dirs. Using only
-        // toolchain.linkRuntimeDirs here dropped dependency runtime dirs, so
-        // dlopen()'d host libs (libGL/libGLX) were unreachable at run time.
-        for (auto& dir : plan.runtimeLibraryDirs) {
+        // Toolchain runtime dirs (glibc/gcc) as before...
+        for (auto& dir : plan.toolchain.linkRuntimeDirs) {
+            runtime_dirs += " -L" + escape_path(dir);
+            runtime_dirs += " -Wl,-rpath," + escape_path(dir);
+        }
+        // ...plus dependency packages' [runtime] library_dirs (e.g.
+        // compat.glx-runtime's host-GL passthrough), so dlopen()'d host libs
+        // (libGL/libGLX) are reachable at run time. Only the dep dirs — NOT the
+        // glibc payload dir — so static/musl links stay clean.
+        for (auto& dir : plan.depRuntimeLibraryDirs) {
             runtime_dirs += " -L" + escape_path(dir);
             runtime_dirs += " -Wl,-rpath," + escape_path(dir);
         }

src/build/plan.cppm

@@ -56,6 +56,11 @@ struct BuildPlan {
     std::vector<CompileUnit>        compileUnits;     // topologically sorted
     std::vector<LinkUnit>           linkUnits;
     std::vector<std::filesystem::path> runtimeLibraryDirs;
+    // ONLY the dependency packages' [runtime] library_dirs (not toolchain/
+    // payload dirs). These are the dirs that must be baked into the produced
+    // binary's RUNPATH (e.g. compat.glx-runtime). Kept separate so static/musl
+    // links don't pull the glibc payload dir.
+    std::vector<std::filesystem::path> depRuntimeLibraryDirs;
     // Aggregated host-runtime requirements from dependency packages'
     // [runtime] metadata. Capability/provider-driven — no platform special-casing
     // in mcpp: providers (e.g. compat.glx-runtime) declare these per platform.
@@ -225,8 +230,9 @@ BuildPlan make_plan(const mcpp::manifest::Manifest&         manifest,
 
     for (auto const& package : packages) {
         for (auto const& dir : package.manifest.runtimeConfig.libraryDirs) {
-            append_unique_path(plan.runtimeLibraryDirs,
-                dir.is_absolute() ? dir : package.root / dir);
+            auto abs = dir.is_absolute() ? dir : package.root / dir;
+            append_unique_path(plan.runtimeLibraryDirs, abs);
+            append_unique_path(plan.depRuntimeLibraryDirs, abs);
         }
         for (auto const& lib : package.manifest.runtimeConfig.dlopenLibs) {
             if (std::ranges::find(plan.runtimeDlopenLibs, lib) == plan.runtimeDlopenLibs.end())

tests/e2e/29_toolchain_partial_versions.sh

@@ -52,9 +52,9 @@ grep -q 'gcc@16.1.0' "$TMP/def2.log" || {
 # ─── Section 2: first-run auto-install ──────────────────────────────────
 # Brand-new MCPP_HOME with no config/default state, brand-new package with no
 # [toolchain] declared — `mcpp build` should auto-install the canonical
-# default (musl-gcc 15.1 for portable static binaries) + use it. We still
-# inherit payloads so CI does not download the same large archives into a
-# throw-away home.
+# default (platform-native glibc gcc — musl-static is opt-in via --target) +
+# use it. We still inherit payloads so CI does not download the same large
+# archives into a throw-away home.
 export MCPP_HOME="$TMP/h2"
 inherit_payloads_only
 configure_e2e_mirror
@@ -75,20 +75,21 @@ fi
 # Must show the friendly first-run banner AND the build must succeed.
 grep -q 'First run' "$TMP/firstrun.log" || {
     cat "$TMP/firstrun.log"; echo "missing First-run banner"; exit 1; }
-grep -q 'gcc@15.1.0-musl' "$TMP/firstrun.log" || {
-    cat "$TMP/firstrun.log"; echo "first run didn't pick gcc@15.1.0-musl as default"; exit 1; }
+grep -q 'gcc@16.1.0' "$TMP/firstrun.log" || {
+    cat "$TMP/firstrun.log"; echo "first run didn't pick glibc gcc@16.1.0 as default"; exit 1; }
 grep -q 'Finished' "$TMP/firstrun.log" || {
     cat "$TMP/firstrun.log"; echo "build did not finish"; exit 1; }
 
-# Built binary must exist, run, AND be statically linked (because the
-# default toolchain is musl, mcpp infers `linkage = static` automatically).
+# Built binary must exist and run. The default toolchain is now platform-native
+# glibc gcc (musl-static is opt-in via --target), so it is dynamically linked.
 binary=$(find target -name hello -type f | head -1)
 [[ -n "$binary" && -x "$binary" ]] || { echo "no hello binary produced"; exit 1; }
-file "$binary" | grep -q 'statically linked' || {
+file "$binary" | grep -q 'statically linked' && {
     file "$binary"
-    echo "first-run build is not statically linked; musl default not propagated"
+    echo "first-run default unexpectedly produced a static binary (glibc default expected)"
     exit 1
 }
+"$binary" >/dev/null 2>&1 || { echo "first-run binary did not run"; exit 1; }
 
 # Second build should be silent on toolchain — no re-install banner.
 "$MCPP" build > "$TMP/secondrun.log" 2>&1 || {