[llvm-branch-commits] [clang] 8820e75 - [clang-repl] Stop interpreter init on action failure (#217147)

[Tobias Hieta via llvm-branch-commits]

Author: Jeaye Wilkerson
Date: 2026-09-05T09:12:04+02:00
New Revision: 8820e75cdd428222df7104fb0efa5c6e63e53bb5

URL: https://github.com/llvm/llvm-project/commit/8820e75cdd428222df7104fb0efa5c6e63e53bb5
DIFF: https://github.com/llvm/llvm-project/commit/8820e75cdd428222df7104fb0efa5c6e63e53bb5.diff

LOG: [clang-repl] Stop interpreter init on action failure (#217147)

`clang::Interpreter` previously ignored the result of its initial
`CompilerInstance::ExecuteAction()` call and always constructed the
`IncrementalParser`. When the initial action failed, the parser could be
created from an invalid compiler state.

In practice, this failure happens if the incremental PCH included has
expired, due to system headers changing. This happens quite regularly,
after system updates, and is affecting jank users.

To fix this, the `Interpreter` now returns an error immediately when the
initial action fails or records a diagnostic error. This allows jank to
add a diagnostic consumer to detect PCH-related errors and rebuild the
PCH as needed.

----
I used Github copilot to help me diagnose and fix the issue. I have
manually reviewed the code, manually executed the test, and have
verified that the fix works locally for jank. I understand the change
completely.

(cherry picked from commit 2ed0f89b61bb6fc136f99a9d1bbcabb84df069f5)

Added: 
    clang/test/Interpreter/stale-pch.cpp

Modified: 
    clang/lib/Interpreter/Interpreter.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index 0536fdcd548a2..ef1ca31538352 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -206,6 +206,15 @@ CreateCI(const llvm::opt::ArgStringList &Argv) {
   return std::move(Clang);
 }
 
+static llvm::Error ExecuteIncrementalAction(CompilerInstance &CI,
+                                            IncrementalAction &Act) {
+  if (!CI.ExecuteAction(Act) || CI.getDiagnostics().hasErrorOccurred()) {
+    return llvm::createStringError(llvm::errc::not_supported,
+                                   "Failed to execute incremental action");
+  }
+  return llvm::Error::success();
+}
+
 } // anonymous namespace
 
 namespace clang {
@@ -349,7 +358,10 @@ Interpreter::Interpreter(std::unique_ptr<CompilerInstance> Instance,
   if (ErrOut)
     return;
 
-  CI->ExecuteAction(*Act);
+  if (llvm::Error E = ExecuteIncrementalAction(*CI, *Act)) {
+    ErrOut = joinErrors(std::move(ErrOut), std::move(E));
+    return;
+  }
 
   IncrParser =
       std::make_unique<IncrementalParser>(*CI, Act.get(), ErrOut, PTUs);
@@ -490,7 +502,8 @@ Interpreter::createWithCUDA(std::unique_ptr<CompilerInstance> CI,
 
   Interp->DeviceAct = std::move(DeviceAct);
 
-  DCI->ExecuteAction(*Interp->DeviceAct);
+  if (llvm::Error E = ExecuteIncrementalAction(*DCI, *Interp->DeviceAct))
+    return std::move(E);
 
   Interp->DeviceCI = std::move(DCI);
 

diff  --git a/clang/test/Interpreter/stale-pch.cpp b/clang/test/Interpreter/stale-pch.cpp
new file mode 100644
index 0000000000000..410a91fe7d8f0
--- /dev/null
+++ b/clang/test/Interpreter/stale-pch.cpp
@@ -0,0 +1,23 @@
+// REQUIRES: host-supports-jit
+// UNSUPPORTED: system-aix
+//
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %if system-windows %{ \
+// RUN: %clang -fmax-type-align=16 -Xclang -fdeprecated-macro -fno-stack-protector -Xclang -fwrapv -Xclang -fblocks -Xclang -fskip-odr-check-in-gmf -fexceptions -fcxx-exceptions -fgnuc-version=0 -target %host-jit-triple -Xclang -fblocks -Xclang -fmax-type-align=8 -Xclang -fincremental-extensions -Xclang -emit-pch -x c++-header -o %t/include.pch %t/include.hpp \
+// RUN: %} \
+// RUN: %else %{ \
+// RUN: %clang -fPIC -fmax-type-align=16 -Xclang -fdeprecated-macro -fno-stack-protector -Xclang -fwrapv -Xclang -fblocks -Xclang -fskip-odr-check-in-gmf -fexceptions -fcxx-exceptions -fgnuc-version=0 -target %host-jit-triple -Xclang -fblocks -Xclang -fmax-type-align=8 -Xclang -fincremental-extensions -Xclang -emit-pch -x c++-header -o %t/include.pch %t/include.hpp \
+// RUN: %}
+// RUN: echo '// changed after PCH creation' >> %t/include.hpp
+//
+// RUN: not clang-repl -Xcc -fgnuc-version=0 -Xcc -fno-stack-protector -Xcc -fwrapv -Xcc -fblocks -Xcc -fskip-odr-check-in-gmf -Xcc -fmax-type-align=8 -Xcc -include-pch -Xcc %t/include.pch < /dev/null 2>&1 | FileCheck %s
+
+//--- include.hpp
+
+int f_pch() { return 5; }
+
+// CHECK: fatal error: file '{{.*}}include.hpp' has been modified since the precompiled header
+// CHECK: clang-repl: Failed to execute incremental action