From fe7f52d689825e01614faa8640d5af6687ed0b6e Mon Sep 17 00:00:00 2001
From: James Lee-Jones <james@lee-jones.co.uk>
Date: Sat, 25 May 2024 22:52:01 +0100
Subject: [PATCH] Avoid mutating variables that require const initialization

We cannot mutate variable declarations that require constant
initialization as Dredd's mutations occur dynamically.

Fixes: #235.
---
 src/libdredd/src/mutate_visitor.cc            | 2 +-
 test/single_file/const_init.cc                | 3 +++
 test/single_file/const_init.cc.expected       | 3 +++
 test/single_file/const_init.cc.noopt.expected | 3 +++
 4 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 test/single_file/const_init.cc
 create mode 100644 test/single_file/const_init.cc.expected
 create mode 100644 test/single_file/const_init.cc.noopt.expected

diff --git a/src/libdredd/src/mutate_visitor.cc b/src/libdredd/src/mutate_visitor.cc
index 284ec16f..80ebdd89 100644
--- a/src/libdredd/src/mutate_visitor.cc
+++ b/src/libdredd/src/mutate_visitor.cc
@@ -118,7 +118,7 @@ bool MutateVisitor::TraverseDecl(clang::Decl* decl) {
     return true;
   }
   if (const auto* var_decl = llvm::dyn_cast<clang::VarDecl>(decl)) {
-    if (var_decl->isConstexpr()) {
+    if (var_decl->isConstexpr() || var_decl->hasConstantInitialization()) {
       // Because Dredd's mutations occur dynamically, they cannot be applied to
       // C++ constexprs, which require compile-time evaluation.
       return true;
diff --git a/test/single_file/const_init.cc b/test/single_file/const_init.cc
new file mode 100644
index 00000000..6934836b
--- /dev/null
+++ b/test/single_file/const_init.cc
@@ -0,0 +1,3 @@
+int main() {
+  [[clang::require_constant_initialization]] static int x = 0;
+}
diff --git a/test/single_file/const_init.cc.expected b/test/single_file/const_init.cc.expected
new file mode 100644
index 00000000..6934836b
--- /dev/null
+++ b/test/single_file/const_init.cc.expected
@@ -0,0 +1,3 @@
+int main() {
+  [[clang::require_constant_initialization]] static int x = 0;
+}
diff --git a/test/single_file/const_init.cc.noopt.expected b/test/single_file/const_init.cc.noopt.expected
new file mode 100644
index 00000000..6934836b
--- /dev/null
+++ b/test/single_file/const_init.cc.noopt.expected
@@ -0,0 +1,3 @@
+int main() {
+  [[clang::require_constant_initialization]] static int x = 0;
+}