[clang] c19cacf - [clang][dataflow] Tighten checking for existence of a function body. (#78163)

[via cfe-commits]

Author: martinboehme
Date: 2024-01-16T12:52:55+01:00
New Revision: c19cacfa34f52b65addeb7239d564b20e3cf2c61

URL: https://github.com/llvm/llvm-project/commit/c19cacfa34f52b65addeb7239d564b20e3cf2c61
DIFF: https://github.com/llvm/llvm-project/commit/c19cacfa34f52b65addeb7239d564b20e3cf2c61.diff

LOG: [clang][dataflow] Tighten checking for existence of a function body. (#78163)

In various places, we would previously call `FunctionDecl::hasBody()`
(which
checks whether any redeclaration of the function has a body, not
necessarily the
one on which `hasBody()` is being called).

This is bug-prone, as a recent bug in Crubit's nullability checker has
shown

([fix](https://github.com/google/crubit/commit/4b01ed0f14d953cda20f92d62256e7365d206b2e),
[fix for the
fix](https://github.com/google/crubit/commit/e0c5d8ddd7d647da483c2ae198ff91d131c12055)).

Instead, we now use `FunctionDecl::doesThisDeclarationHaveABody()`
which, as the
name implies, checks whether the specific redeclaration it is being
called on
has a body.

Alternatively, I considered being more lenient and "canonicalizing" to
the
`FunctionDecl` that has the body if the `FunctionDecl` being passed is a
different redeclaration. However, this also risks hiding bugs: A caller
might
inadverently perform the analysis for all redeclarations of a function
and end
up duplicating work without realizing it. By accepting only the
redeclaration
that contains the body, we prevent this.

I've checked, and all clients that I'm aware of do currently pass in the
redeclaration that contains the function body. Typically this is because
they
use the `ast_matchers::hasBody()` matcher which, unlike
`FunctionDecl::hasBody()`, only matches for the redeclaration containing
the
body.

Added: 
    

Modified: 
    clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
    clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
    clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
    clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
    clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h b/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
index 768387a121b920a..405e93287a05d38 100644
--- a/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
+++ b/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
@@ -32,7 +32,8 @@ namespace dataflow {
 class ControlFlowContext {
 public:
   /// Builds a ControlFlowContext from a `FunctionDecl`.
-  /// `Func.hasBody()` must be true, and `Func.isTemplated()` must be false.
+  /// `Func.doesThisDeclarationHaveABody()` must be true, and
+  /// `Func.isTemplated()` must be false.
   static llvm::Expected<ControlFlowContext> build(const FunctionDecl &Func);
 
   /// Builds a ControlFlowContext from an AST node. `D` is the function in which

diff  --git a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
index e8c27d6c12038b2..1543f900e401d6d 100644
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
@@ -172,7 +172,8 @@ class Environment {
   ///
   /// Requirements:
   ///
-  ///  The function must have a body.
+  ///  The function must have a body, i.e.
+  ///  `FunctionDecl::doesThisDecalarationHaveABody()` must be true.
   void initialize();
 
   /// Returns a new environment that is a copy of this one.

diff  --git a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
index 56246066e4aa13a..c9ebffe6f378019 100644
--- a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
+++ b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
@@ -69,7 +69,7 @@ static llvm::BitVector findReachableBlocks(const CFG &Cfg) {
 
 llvm::Expected<ControlFlowContext>
 ControlFlowContext::build(const FunctionDecl &Func) {
-  if (!Func.hasBody())
+  if (!Func.doesThisDeclarationHaveABody())
     return llvm::createStringError(
         std::make_error_code(std::errc::invalid_argument),
         "Cannot analyze function without a body");

diff  --git a/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp b/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
index d95b3324ef6b2ae..f4c4af022f51f6b 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
@@ -298,7 +298,7 @@ DataflowAnalysisContext::getControlFlowContext(const FunctionDecl *F) {
   if (It != FunctionContexts.end())
     return &It->second;
 
-  if (F->hasBody()) {
+  if (F->doesThisDeclarationHaveABody()) {
     auto CFCtx = ControlFlowContext::build(*F);
     // FIXME: Handle errors.
     assert(CFCtx);

diff  --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
index 96fe6df88dbb9f7..a50ee57a3c11b44 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -386,7 +386,7 @@ void Environment::initialize() {
     return;
 
   if (const auto *FuncDecl = dyn_cast<FunctionDecl>(DeclCtx)) {
-    assert(FuncDecl->getBody() != nullptr);
+    assert(FuncDecl->doesThisDeclarationHaveABody());
 
     initFieldsGlobalsAndFuncs(FuncDecl);
 
@@ -426,7 +426,7 @@ void Environment::initialize() {
 // FIXME: Add support for resetting globals after function calls to enable
 // the implementation of sound analyses.
 void Environment::initFieldsGlobalsAndFuncs(const FunctionDecl *FuncDecl) {
-  assert(FuncDecl->getBody() != nullptr);
+  assert(FuncDecl->doesThisDeclarationHaveABody());
 
   FieldSet Fields;
   llvm::DenseSet<const VarDecl *> Vars;