[clang][clangd] Ensure the stack bottom before building AST

`clang::runWithSufficientStackSpace` requires the address of the
initial stack bottom to prevent potential stack overflows.

In addition, add a fallback to ASTFrontendAction in case any client
forgets to call it when not through CompilerInstance::ExecuteAction,
which is rare.

Fixes https://github.com/clangd/clangd/issues/1745.

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D158967

1 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index f14557c..2da25be 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -15,6 +15,7 @@
 #include "clang/Basic/FileEntry.h"
 #include "clang/Basic/LangStandard.h"
 #include "clang/Basic/Sarif.h"
+#include "clang/Basic/Stack.h"
 #include "clang/Frontend/ASTUnit.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
@@ -1155,6 +1156,10 @@ void ASTFrontendAction::ExecuteAction() {
   CompilerInstance &CI = getCompilerInstance();
   if (!CI.hasPreprocessor())
     return;
+  // This is a fallback: If the client forgets to invoke this, we mark the
+  // current stack as the bottom. Though not optimal, this could help prevent
+  // stack overflow during deep recursion.
+  clang::noteBottomOfStack();
 
   // FIXME: Move the truncation aspect of this into Sema, we delayed this till
   // here so the source manager would be initialized.