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Toolchain/Clang: Support using libstdc++ as the C++ standard library

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This will come in handy if we want to use the LLVM port with a GNU host
compiler.

As of version 13, libc++ uses `__attribute__((using_if_exists))` to
import global LibC functions into the `std` namespace, which allows some
symbols to be absent. GCC does not support this attribute, so it fails
to build libc++ due to some obscure `wchar.h` functions. This means that
cross-compiling libc++ is not possible; and on-target builds would be
tedious, so we'll be better off using the toolchain's `libstdc++`.
This commit is contained in:
Daniel Bertalan 2021-11-20 16:48:14 +01:00 committed by Brian Gianforcaro
parent ce3b219021
commit b1f6bfca7f
Notes: sideshowbarker 2024-07-18 00:35:10 +09:00 
Author: https://github.com/BertalanD
Commit: https://github.com/SerenityOS/serenity/commit/b1f6bfca7fb
Pull-request: https://github.com/SerenityOS/serenity/pull/10996
Reviewed-by: https://github.com/timschumi ✅
1 changed files with 53 additions and 7 deletions
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60
Toolchain/Patches/llvm.patch
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@ -136,10 +136,10 @@ index 58ae08a38..8e9a3fee6 100644
options::OPT_foperator_names, false))
diff --git a/clang/lib/Driver/ToolChains/Serenity.cpp b/clang/lib/Driver/ToolChains/Serenity.cpp
new file mode 100644
index 000000000..461f55ad3
index 000000000..4d653d86f
--- /dev/null
+++ b/clang/lib/Driver/ToolChains/Serenity.cpp
@@ -0,0 +1,281 @@
@@ -0,0 +1,327 @@
+//===---- Serenity.cpp - SerenityOS ToolChain Implementation ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@ -158,6 +158,7 @@ index 000000000..461f55ad3
+#include "clang/Driver/SanitizerArgs.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Support/VirtualFileSystem.h"
+#include <string>
+
+using namespace clang::driver;
+using namespace clang::driver::toolchains;
@ -348,28 +349,73 @@ index 000000000..461f55ad3
+
+ addSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/usr/local/include");
+ addSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/usr/include");
+}
+
+static std::string getLibStdCXXVersion(const Driver &D, StringRef IncludePath) {
+ SmallString<128> Path(IncludePath);
+ llvm::sys::path::append(Path, "c++");
+
+ std::error_code EC;
+ std::tuple<int, int, int> Newest{0, 0, 0};
+ std::string Result;
+
+ for (llvm::vfs::directory_iterator LI = D.getVFS().dir_begin(Path, EC), LE;
+ !EC && LI != LE; LI = LI.increment(EC)) {
+ StringRef VersionText = llvm::sys::path::filename(LI->path());
+
+ // This is libc++
+ if (VersionText[0] == 'v')
+ continue;
+
+ llvm::SmallVector<StringRef, 3> Parts;
+ VersionText.split(Parts, '.');
+
+ // SerenityOS always builds GCC with <major>.<minor>.<patch> versions
+ if (Parts.size() < 3)
+ continue;
+
+ std::tuple<int, int, int> Current;
+ if (!llvm::to_integer(Parts[0], std::get<0>(Current)))
+ continue;
+ if (!llvm::to_integer(Parts[1], std::get<1>(Current)))
+ continue;
+ if (!llvm::to_integer(Parts[2], std::get<2>(Current)))
+ continue;
+
+ if (Current > Newest) {
+ Newest = Current;
+ Result = VersionText.str();
+ }
+ }
+ return Result;
+}
+
+void Serenity::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
+ ArgStringList &CC1Args) const {
+ if (DriverArgs.hasArg(options::OPT_nostdinc, options::OPT_nostdincxx,
+ +options::OPT_nostdlibinc))
+ options::OPT_nostdlibinc))
+ return;
+
+ if (GetCXXStdlibType(DriverArgs) != ToolChain::CST_Libcxx)
+ llvm_unreachable("Only libc++ is supported on the Serenity target");
+ const auto StdLib = GetCXXStdlibType(DriverArgs);
+
+ const Driver &D = getDriver();
+ std::string SysRoot = computeSysRoot();
+ std::string Target = getTripleString();
+
+ auto AddIncludePath = [&](std::string Path) {
+ std::string Version = detectLibcxxVersion(Path);
+ std::string Version = StdLib == CXXStdlibType::CST_Libstdcxx
+ ? getLibStdCXXVersion(D, Path)
+ : detectLibcxxVersion(Path);
+ if (Version.empty())
+ return false;
+
+ std::string TargetDir = Path + "/" + Target + "/c++/" + Version;
+ std::string TargetDir;
+ if (StdLib == CXXStdlibType::CST_Libstdcxx) {
+ TargetDir = Path + "/c++/" + Version + "/" + Target;
+ } else {
+ TargetDir = Path + "/" + Target + "/c++/" + Version;
+ }
+
+ if (D.getVFS().exists(TargetDir))
+ addSystemInclude(DriverArgs, CC1Args, TargetDir);
+