[clang-tools-extra] [clangd] Log environment variables that influence compilation at startup (PR #204990)

[Akshay Kumar Dubey via cfe-commits]

https://github.com/akshaydubey05 updated https://github.com/llvm/llvm-project/pull/204990

>From b1d3a777edf662990fc05c4259908e5645c49af5 Mon Sep 17 00:00:00 2001
From: akshaydubey05 <akshaydubey05 at gmail.com>
Date: Sun, 21 Jun 2026 21:57:09 +0530
Subject: [PATCH 1/2] [clangd] Log environment variables that influence
 compilation at startup

Print env vars like INCLUDE, CPATH, LIBRARY_PATH etc. at startup to help
diagnose missing system include issues, especially on Windows.

Fixes https://github.com/clangd/clangd/issues/2657
---
 clang-tools-extra/clangd/tool/ClangdMain.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
index 549b1ae8d7980..af6022856339b 100644
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -912,6 +912,18 @@ clangd accepts flags on the commandline, and in the CLANGD_FLAGS environment var
     log("argv[{0}]: {1}", I, argv[I]);
   if (auto EnvFlags = llvm::sys::Process::GetEnv(FlagsEnvVar))
     log("{0}: {1}", FlagsEnvVar, *EnvFlags);
+  // Log environment variables that influence how clangd finds system headers.
+  // This helps diagnose missing-include issues, especially on Windows.
+  for (const char *EnvVar : {
+           // MSVC environment variables (set by vcvarsall.bat)
+           "INCLUDE", "LIB", "LIBPATH", "CL", "_CL_",
+           // GCC/Clang environment variables
+           "CPATH", "C_INCLUDE_PATH", "CPLUS_INCLUDE_PATH",
+           "OBJC_INCLUDE_PATH", "LIBRARY_PATH", "GCC_EXEC_PREFIX",
+       }) {
+    if (auto Val = llvm::sys::Process::GetEnv(EnvVar))
+      log("Env {0}: {1}", EnvVar, *Val);
+  }
 
   ClangdLSPServer::Options Opts;
   Opts.UseDirBasedCDB = (CompileArgsFrom == FilesystemCompileArgs);

>From 39108cbfae6dd92bb4c9dd00335ede2c0941c6a3 Mon Sep 17 00:00:00 2001
From: akshaydubey05 <akshaydubey05 at gmail.com>
Date: Sun, 21 Jun 2026 22:08:40 +0530
Subject: [PATCH 2/2] clang-format: put each env var string on its own line

---
 clang-tools-extra/clangd/tool/ClangdMain.cpp | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
index af6022856339b..13fe4d3911731 100644
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -916,10 +916,18 @@ clangd accepts flags on the commandline, and in the CLANGD_FLAGS environment var
   // This helps diagnose missing-include issues, especially on Windows.
   for (const char *EnvVar : {
            // MSVC environment variables (set by vcvarsall.bat)
-           "INCLUDE", "LIB", "LIBPATH", "CL", "_CL_",
+           "INCLUDE",
+           "LIB",
+           "LIBPATH",
+           "CL",
+           "_CL_",
            // GCC/Clang environment variables
-           "CPATH", "C_INCLUDE_PATH", "CPLUS_INCLUDE_PATH",
-           "OBJC_INCLUDE_PATH", "LIBRARY_PATH", "GCC_EXEC_PREFIX",
+           "CPATH",
+           "C_INCLUDE_PATH",
+           "CPLUS_INCLUDE_PATH",
+           "OBJC_INCLUDE_PATH",
+           "LIBRARY_PATH",
+           "GCC_EXEC_PREFIX",
        }) {
     if (auto Val = llvm::sys::Process::GetEnv(EnvVar))
       log("Env {0}: {1}", EnvVar, *Val);