Merge pull request #7688 from xmake-io/runtime

improve clang static libc++ runtimes

3 files changed, 102 insertions, 8 deletions

diff --git a/xmake/languages/c++/xmake.lua b/xmake/languages/c++/xmake.lua
index b94a073b8..42ddc2884 100644
--- a/xmake/languages/c++/xmake.lua
+++ b/xmake/languages/c++/xmake.lua
@@ -60,8 +60,7 @@ language("c++")
         ,   "toolchain.sysincludedirs"
         }
     ,   binary = {
-            "target.runtimes"
-        ,   "config.linkdirs"
+            "config.linkdirs"
         ,   "config.frameworkdirs"
         ,   "target.linkdirs"
         ,   "target.frameworkdirs"
@@ -79,13 +78,16 @@ language("c++")
         ,   "config.frameworks"
         ,   "target.frameworks"
         ,   "toolchain.frameworks"
+        -- runtimes may link libc++.a/libc++abi.a explicitly, so it must come after the
+        -- object files and user links, but before the syslinks it depends on (e.g. pthread)
+        -- @see https://github.com/xmake-io/xmake/issues/7442
+        ,   "target.runtimes"
         ,   "config.syslinks"
         ,   "target.syslinks"
         ,   "toolchain.syslinks"
         }
     ,   shared = {
-            "target.runtimes"
-        ,   "config.linkdirs"
+            "config.linkdirs"
         ,   "config.frameworkdirs"
         ,   "target.linkdirs"
         ,   "target.frameworkdirs"
@@ -103,6 +105,8 @@ language("c++")
         ,   "config.frameworks"
         ,   "target.frameworks"
         ,   "toolchain.frameworks"
+        -- @see https://github.com/xmake-io/xmake/issues/7442
+        ,   "target.runtimes"
         ,   "config.syslinks"
         ,   "target.syslinks"
         ,   "toolchain.syslinks"
diff --git a/xmake/modules/core/tools/clang.lua b/xmake/modules/core/tools/clang.lua
index d9d6512ee..c264f6656 100644
--- a/xmake/modules/core/tools/clang.lua
+++ b/xmake/modules/core/tools/clang.lua
@@ -192,6 +192,19 @@ function _has_static_libstdcxx(self)
     return has_static_libstdcxx
 end
 
+-- has -nostdlib++? (disable the automatic c++ runtime link, so we can link libc++/libc++abi explicitly)
+function _has_nostdlibxx(self)
+    local has_nostdlibxx = _g._HAS_NOSTDLIBXX
+    if has_nostdlibxx == nil then
+        if self:has_flags("-nostdlib++ -Werror", "ldflags", {flagskey = "clang_nostdlibxx"}) then
+            has_nostdlibxx = true
+        end
+        has_nostdlibxx = has_nostdlibxx or false
+        _g._HAS_NOSTDLIBXX = has_nostdlibxx
+    end
+    return has_nostdlibxx
+end
+
 -- make the runtime flag
 -- @see https://github.com/xmake-io/xmake/issues/3546
 function nf_runtime(self, runtime, opt)
@@ -284,9 +297,36 @@ function nf_runtime(self, runtime, opt)
                         end
                     end
                 end
-                if runtime:endswith("_static") and _has_static_libstdcxx(self) then
-                    maps["c++_static"] = table.join(maps["c++_static"], "-static-libstdc++")
-                    maps["stdc++_static"] = table.join(maps["stdc++_static"], "-static-libstdc++")
+                if runtime:endswith("_static") then
+                    -- -static-libstdc++ only pulls in libc++.a, not libc++abi.a, so the libc++abi
+                    -- symbols (typeinfo, __cxa_*) stay undefined and the link fails, especially
+                    -- once c++ modules reference more of libc++.
+                    --
+                    -- if we can locate both static archives, link them explicitly in a group
+                    -- (they reference each other) and disable the driver's automatic c++ runtime
+                    -- with -nostdlib++, otherwise (bundled abi) fall back to -static-libstdc++.
+                    --
+                    -- note: target.runtimes is ordered right before the syslinks in the c++ link
+                    -- order, so these archives are placed after the object files / user links.
+                    -- @see https://github.com/xmake-io/xmake/issues/7442, https://github.com/xmake-io/xmake/issues/7656
+                    if llvm_dirs.libcxx_static and llvm_dirs.libcxxabi_static and _has_nostdlibxx(self) then
+                        local cxxlibs = {llvm_dirs.libcxx_static, llvm_dirs.libcxxabi_static}
+                        -- apple ld64 does not support --start-group, it always rescans archives
+                        if not self:is_plat("macosx", "iphoneos", "watchos", "appletvos", "applexros") then
+                            cxxlibs = table.join("-Wl,--start-group", cxxlibs, "-Wl,--end-group")
+                        end
+                        -- -stdlib=libc++ is unused when linking with -nostdlib++, remove it to avoid
+                        -- the `argument unused during compilation` warning
+                        local ldflags = table.remove_if(table.wrap(maps["c++_static"]), function (_, flag)
+                            return flag == "-stdlib=libc++"
+                        end)
+                        maps["c++_static"] = table.join(ldflags, "-nostdlib++", cxxlibs)
+                    elseif _has_static_libstdcxx(self) then
+                        maps["c++_static"] = table.join(maps["c++_static"], "-static-libstdc++")
+                    end
+                    if _has_static_libstdcxx(self) then
+                        maps["stdc++_static"] = table.join(maps["stdc++_static"], "-static-libstdc++")
+                    end
                 end
             end
         end
diff --git a/xmake/modules/private/utils/toolchain.lua b/xmake/modules/private/utils/toolchain.lua
index c2840a591..bd673fa0c 100644
--- a/xmake/modules/private/utils/toolchain.lua
+++ b/xmake/modules/private/utils/toolchain.lua
@@ -343,6 +343,25 @@ function map_linkflags_for_package(package, targetkind, sourcekinds, name, value
     return flags
 end
 
+-- ask the clang driver for the absolute path of the given library
+--
+-- clang knows its own library search paths, e.g. the per-target runtime directory
+-- (`lib/<target-triple>/libc++.a`), and it also works when the toolchain has no `--sdk=/xxx/llvm`.
+--
+-- it just echoes back the given filename if the library does not exist,
+-- so we only accept an existing absolute path.
+function _get_llvm_libfile(toolchain, clang, libname, opt)
+    local argv = table.wrap(get_clang_target_flags(toolchain))
+    table.insert(argv, "-print-file-name=" .. libname)
+    local libfile = try {function () return os.iorunv(clang, argv, {envs = opt.envs}) end}
+    if libfile then
+        libfile = path.normalize(libfile:trim())
+        if path.is_absolute(libfile) and os.isfile(libfile) then
+            return libfile
+        end
+    end
+end
+
 -- Check and cache llvm/clang driver info (e.g. -print-resource-dir/-print-target-triple) in toolchain:config().
 -- It must be collected during toolchain on_check so that toolchain on_load can use it without running clang again.
 -- @see https://github.com/xmake-io/xmake/issues/7337#issuecomment-3942499208
@@ -370,6 +389,17 @@ function check_llvm_info(toolchain, clang, opt)
             toolchain:config_set("llvm_target_triple", target_triple)
         end
     end
+
+    -- the static c++ runtime archives, they may be in the per-target runtime directory,
+    -- e.g. `lib/x86_64-unknown-linux-gnu/libc++.a`
+    -- @see https://github.com/xmake-io/xmake/issues/7442
+    for libname, configname in pairs({["libc++.a"] = "llvm_libcxx_static", ["libc++abi.a"] = "llvm_libcxxabi_static"}) do
+        local libfile = _get_llvm_libfile(toolchain, clang, libname, opt)
+        if libfile then
+            dprint("checking for llvm %s ... %s", libname, libfile)
+            toolchain:config_set(configname, libfile)
+        end
+    end
 end
 
 -- get llvm sdk resource directory
@@ -457,6 +487,11 @@ function get_llvm_dirs(toolchain)
         end
 
         local bindir, libdir, cxxlibdir, includedir, cxxincludedir, resourcedir, rtdir, rtlink, rtlibdir
+
+        -- the clang driver has already resolved the static c++ runtime archives on check
+        -- @see check_llvm_info
+        local libcxx_static = toolchain:config("llvm_libcxx_static")
+        local libcxxabi_static = toolchain:config("llvm_libcxxabi_static")
         if rootdir then
             bindir = path.join(rootdir, "bin")
             bindir = os.isdir(bindir) and bindir or nil
@@ -476,6 +511,19 @@ function get_llvm_dirs(toolchain)
                 end
             end
 
+            -- fallback to search the static c++ runtime archives in the library directories
+            if libdir and not (libcxx_static and libcxxabi_static) then
+                local staticdirs = cxxlibdir and {cxxlibdir, libdir} or {libdir}
+                for _, dir in ipairs(staticdirs) do
+                    if not libcxx_static and os.isfile(path.join(dir, "libc++.a")) then
+                        libcxx_static = path.join(dir, "libc++.a")
+                    end
+                    if not libcxxabi_static and os.isfile(path.join(dir, "libc++abi.a")) then
+                        libcxxabi_static = path.join(dir, "libc++abi.a")
+                    end
+                end
+            end
+
             includedir = path.join(rootdir, "include")
             includedir = os.isdir(includedir) and includedir or nil
 
@@ -502,7 +550,9 @@ function get_llvm_dirs(toolchain)
                      resourcedir = resourcedir,
                      rtdir = rtdir,
                      rtlibdir = rtlibdir,
-                     rtlink = rtlink }
+                     rtlink = rtlink,
+                     libcxx_static = libcxx_static,
+                     libcxxabi_static = libcxxabi_static }
         memcache:set(cachekey, llvm_dirs)
       end
       return llvm_dirs