clangd: support -stdlib= flags from compile_commands.json.

[cjc25]

The --stdlib flag can affect the system headers used by clang during compilation. By default, clang will use the platform-installed C++ standard headers, but with --stdlib=libc++, clang can use headers included in the distribution for its libc++ implementation.

Prior to this patch, if compile_commands.json specified -stdlib=libc++ or an equivalent form and --query-driver took effect, clangd would ignore stdlib and index based on the platform's headers. When these mismatch, e.g. due to version differences, clangd's completions and the actual compilation can differ.

fixes clangd/clangd#1784

[llvmbot]

@llvm/pr-subscribers-clangd

Author: Chris Carlon (cjc25)

Changes

The --stdlib flag can affect the system headers used by clang during compilation. By default, clang will use the platform-installed C++ standard headers, but with --stdlib=libc++, clang can use headers included in the distribution for its libc++ implementation.

Prior to this patch, if compile_commands.json specified -stdlib=libc++ or an equivalent form and --query-driver took effect, clangd would ignore stdlib and index based on the platform's headers. When these mismatch, e.g. due to version differences, clangd's completions and the actual compilation can differ.

fixes clangd/clangd#1784

---

Full diff: https://github.com/llvm/llvm-project/pull/69283.diff

2 Files Affected:

• (modified) clang-tools-extra/clangd/SystemIncludeExtractor.cpp (+14-2)
• (modified) clang-tools-extra/clangd/test/system-include-extractor.test (+3-2)

diff --git a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
index 74bae786425c829..158d4a940dee333 100644
--- a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
+++ b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
@@ -88,12 +88,14 @@ struct DriverArgs {
   std::string Sysroot;
   std::string ISysroot;
   std::string Target;
+  std::string Stdlib;
 
   bool operator==(const DriverArgs &RHS) const {
     return std::tie(Driver, StandardIncludes, StandardCXXIncludes, Lang,
-                    Sysroot, ISysroot, Target) ==
+                    Sysroot, ISysroot, Target, Stdlib) ==
            std::tie(RHS.Driver, RHS.StandardIncludes, RHS.StandardCXXIncludes,
-                    RHS.Lang, RHS.Sysroot, RHS.ISysroot, RHS.Target);
+                    RHS.Lang, RHS.Sysroot, RHS.ISysroot, RHS.Target,
+                    RHS.Stdlib);
   }
 
   DriverArgs(const tooling::CompileCommand &Cmd, llvm::StringRef File) {
@@ -136,6 +138,13 @@ struct DriverArgs {
       } else if (Arg.consume_front("-target")) {
         if (Arg.empty() && I + 1 < E)
           Target = Cmd.CommandLine[I + 1];
+      } else if (Arg.consume_front("--stdlib")) {
+        if (Arg.consume_front("="))
+          Stdlib = Arg.str();
+        else if (Arg.empty() && I + 1 < E)
+          Stdlib = Cmd.CommandLine[I + 1];
+      } else if (Arg.consume_front("-stdlib=")) {
+        Stdlib = Arg.str();
       }
     }
 
@@ -175,6 +184,8 @@ struct DriverArgs {
       Args.append({"-isysroot", ISysroot});
     if (!Target.empty())
       Args.append({"-target", Target});
+    if (!Stdlib.empty())
+      Args.append({"--stdlib", Stdlib});
     return Args;
   }
 
@@ -203,6 +214,7 @@ template <> struct DenseMapInfo<DriverArgs> {
         Val.Driver,
         Val.StandardIncludes,
         Val.StandardCXXIncludes,
+        Val.Stdlib,
         Val.Lang,
         Val.Sysroot,
         Val.ISysroot,
diff --git a/clang-tools-extra/clangd/test/system-include-extractor.test b/clang-tools-extra/clangd/test/system-include-extractor.test
index 66882e424bb9216..cbb3018b2fa7349 100644
--- a/clang-tools-extra/clangd/test/system-include-extractor.test
+++ b/clang-tools-extra/clangd/test/system-include-extractor.test
@@ -18,6 +18,7 @@
 # RUN: echo '[ -z "${args##*"--sysroot /my/sysroot/path"*}" ] || exit' >> %t.dir/bin/my_driver.sh
 # RUN: echo '[ -z "${args##*"-isysroot /isysroot"*}" ] || exit' >> %t.dir/bin/my_driver.sh
 # RUN: echo '[ -z "${args##*"-target arm-linux-gnueabihf"*}" ] || exit' >> %t.dir/bin/my_driver.sh
+# RUN: echo '[ -z "${args##*"--stdlib libc++"*}" ] || exit' >> %t.dir/bin/my_driver.sh
 # RUN: echo 'echo line to ignore >&2' >> %t.dir/bin/my_driver.sh
 # RUN: echo 'printf "Target: arm-linux-gnueabihf\r\n" >&2' >> %t.dir/bin/my_driver.sh
 # RUN: echo 'printf "#include <...> search starts here:\r\n" >&2' >> %t.dir/bin/my_driver.sh
@@ -37,7 +38,7 @@
 
 # Generate a compile_commands.json that will query the mock driver we've
 # created. Which should add a.h and b.h into include search path.
-# RUN: echo '[{"directory": "%/t.dir", "command": "my_driver.sh the-file.cpp --target=arm-linux-gnueabihf -nostdinc --sysroot /my/sysroot/path -isysroot/isysroot", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
+# RUN: echo '[{"directory": "%/t.dir", "command": "my_driver.sh the-file.cpp --target=arm-linux-gnueabihf -nostdinc --sysroot /my/sysroot/path -isysroot/isysroot -stdlib=libc++", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
 
 # RUN: sed -e "s|INPUT_DIR|%/t.dir|g" %s > %t.test.1
 # On Windows, we need the URI in didOpen to look like "uri":"file:///C:/..."
@@ -75,7 +76,7 @@
 {"jsonrpc":"2.0","method":"exit"}
 
 # Generate a different compile_commands.json which does not point to the mock driver
-# RUN: echo '[{"directory": "%/t.dir", "command": "gcc the-file.cpp --target=arm-linux-gnueabihf -nostdinc --sysroot /my/sysroot/path -isysroot/isysroot", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
+# RUN: echo '[{"directory": "%/t.dir", "command": "gcc the-file.cpp --target=arm-linux-gnueabihf -nostdinc --sysroot /my/sysroot/path -isysroot/isysroot -stdlib=libc++", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
 
 # Generate a clangd config file which points to the mock driver instead
 # RUN: echo 'CompileFlags:' > %t.dir/.clangd

[HighCommander4]

nit: it looks like the previous patch which introduced Target forgot to add it here, could you add please?

[cjc25]

Done, and resorted these to match the order in DriverArgs definition so it'll be easier to tell when things are missing in the future.

[HighCommander4]

LGTM