[clang] [Preprocessor] Do not expand macros if the input is already preprocessed (PR #137665)

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Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/137665 at github.com>


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Juan Manuel Martinez Caamaño (jmmartinez)

<details>
<summary>Changes</summary>

This is a draft while I'm trying to figure out what's left to do.

This has issues with the test `Modules/initializers.cpp`.
The function `CompilerInstance::createModuleFromSource` creates  a `FrontendInput` that "is preprocessed" from the preprocessed source string that is passed as argument (the module contents). However, this does not seem preprocessed (at least for this test).

https://github.com/llvm/llvm-project/blob/ca21508080031c3eda1c6085f1de9cc26be4c336/clang/lib/Frontend/CompilerInstance.cpp#L2243

I'm not familiar with modules and I'm not sure if it's this patch, or the test that has issues.

Other failures are fixed with https://github.com/llvm/llvm-project/pull/137623

---
Full diff: https://github.com/llvm/llvm-project/pull/137665.diff


3 Files Affected:

- (modified) clang/include/clang/Lex/Preprocessor.h (+5) 
- (modified) clang/lib/Frontend/InitPreprocessor.cpp (+7) 
- (added) clang/test/Preprocessor/preprocess-cpp-output.c (+10) 


``````````diff
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index f2dfd3a349b8b..63774e48a468b 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -1831,6 +1831,11 @@ class Preprocessor {
     MacroExpansionInDirectivesOverride = true;
   }
 
+  void SetDisableMacroExpansion() {
+    DisableMacroExpansion = true;
+    MacroExpansionInDirectivesOverride = false;
+  }
+
   /// Peeks ahead N tokens and returns that token without consuming any
   /// tokens.
   ///
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 1f297f228fc1b..6693cfb469f82 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1556,6 +1556,13 @@ void clang::InitializePreprocessor(Preprocessor &PP,
                                    const PCHContainerReader &PCHContainerRdr,
                                    const FrontendOptions &FEOpts,
                                    const CodeGenOptions &CodeGenOpts) {
+
+  if (all_of(FEOpts.Inputs,
+             [](const FrontendInputFile &FI) { return FI.isPreprocessed(); })) {
+    PP.SetDisableMacroExpansion();
+    return;
+  }
+
   const LangOptions &LangOpts = PP.getLangOpts();
   std::string PredefineBuffer;
   PredefineBuffer.reserve(4080);
diff --git a/clang/test/Preprocessor/preprocess-cpp-output.c b/clang/test/Preprocessor/preprocess-cpp-output.c
new file mode 100644
index 0000000000000..2c180601e30ac
--- /dev/null
+++ b/clang/test/Preprocessor/preprocess-cpp-output.c
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -E -x c %s | FileCheck %s --check-prefixes=EXPANDED
+// RUN: %clang_cc1 -E -x cpp-output %s | FileCheck %s --check-prefixes=NOT-EXPANDED
+
+// EXPANDED: void __attribute__((__attribute__((always_inline)))) foo()
+// NOT-EXPANDED: void __attribute__((always_inline)) foo()
+
+#define always_inline __attribute__((always_inline))
+void __attribute__((always_inline)) foo() {
+    return 4;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/137665