llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-static-analyzer-1
Author: None (Tedlion)
<details>
<summary>Changes</summary>
For the following code:
struct B{
int i :2;
int :30; // unnamed bit-field
};
extern void consume_B(B);
void bitfield_B_init(void) {
B b1;
b1.i = 1; // b1 is initialized
consume_B(b1);
}
The current clang static analyzer gives false positive warning "Passed-by-value
struct argument contains uninitialized data (e.g., field: '')
[core.CallAndMessage]" when taking the source as C code. However, no such
warning is generated when clang takes the source as C++ code.
After comparing the CallAndMessageChecker's different behaviors between C and
C++, the reason is found: When FindUninitializedField::Find(const
TypedValueRegion *R) is invoked, the concrete type of R is different. In C,
'b1' is considered to be a 'StackLocalsSpaceRegion', which makes
'StoreMgr.getBinding(store, loc::MemRegionVal(FR))' return an 'UndefinedVal'.
While in c++, 'b1' is considered to be a 'tackArgumentsSpaceRegion', which
finally makes the 'getBinding' return a SymbolVal. **I am not quite sure about
the region difference, maybe in C++ there is an implicit copy constructor
function?**
Anyway, the unnamed bit-field is undefined, for it cannot be written unless
using memory operation such
as 'memset'. So a special check FD->isUnnamedBitField() is added in
RegionStoreManager::getBindingForField in file RegionStore.cpp.
To handle the false warning, a check isUnnamedBitField is also added in
FindUninitializedField::Find in file CallAndMessageChecker.cpp.
Testcases of unnamed bit-field are added in file call-and-message.c and
call-and-message.cpp. **I do not know what to do on the hash, so it may be
updated?**
---
Full diff: https://github.com/llvm/llvm-project/pull/145066.diff
4 Files Affected:
- (modified) clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp (+1-1)
- (modified) clang/lib/StaticAnalyzer/Core/RegionStore.cpp (+14-1)
- (modified) clang/test/Analysis/call-and-message.c (+26-1)
- (modified) clang/test/Analysis/call-and-message.cpp (+16)
``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
b/clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
index 86476b32309c3..677cc6ee57ad2 100644
--- a/clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
@@ -259,7 +259,7 @@ class FindUninitializedField {
if (T->getAsStructureType()) {
if (Find(FR))
return true;
- } else {
+ } else if (!I->isUnnamedBitField()){
SVal V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
if (V.isUndef())
return true;
diff --git a/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
b/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
index 388034b087789..1208036700f32 100644
--- a/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
+++ b/clang/lib/StaticAnalyzer/Core/RegionStore.cpp
@@ -2122,8 +2122,21 @@ SVal
RegionStoreManager::getBindingForField(RegionBindingsConstRef B,
if (const std::optional<SVal> &V = B.getDirectBinding(R))
return *V;
- // If the containing record was initialized, try to get its constant value.
+ // UnnamedBitField is always Undefined unless using memory operation such
+ // as 'memset'.
+ // For example, for code
+ // typedef struct {
+ // int i :2;
+ // int :30; // unnamed bit-field
+ // } A;
+ // A a = {1};
+ // The bits of the unnamed bit-field in local variable a can be anything.
const FieldDecl *FD = R->getDecl();
+ if (FD->isUnnamedBitField()) {
+ return UndefinedVal();
+ }
+
+ // If the containing record was initialized, try to get its constant value.
QualType Ty = FD->getType();
const MemRegion* superR = R->getSuperRegion();
if (const auto *VR = dyn_cast<VarRegion>(superR)) {
diff --git a/clang/test/Analysis/call-and-message.c
b/clang/test/Analysis/call-and-message.c
index b79ec8c344b6c..e2fba55d3343d 100644
--- a/clang/test/Analysis/call-and-message.c
+++ b/clang/test/Analysis/call-and-message.c
@@ -1,12 +1,19 @@
// RUN: %clang_analyze_cc1 %s -verify \
// RUN: -analyzer-checker=core \
// RUN: -analyzer-config core.CallAndMessage:ArgPointeeInitializedness=true \
+// RUN: -analyzer-config core.CallAndMessage:ArgInitializedness=false \
// RUN: -analyzer-output=plist -o %t.plist
// RUN: cat %t.plist | FileCheck %s
// RUN: %clang_analyze_cc1 %s -verify=no-pointee \
// RUN: -analyzer-checker=core \
-// RUN: -analyzer-config core.CallAndMessage:ArgPointeeInitializedness=false
+// RUN: -analyzer-config core.CallAndMessage:ArgPointeeInitializedness=false
\
+// RUN: -analyzer-config core.CallAndMessage:ArgInitializedness=false
+
+// RUN: %clang_analyze_cc1 %s -verify=arg-init \
+// RUN: -analyzer-checker=core \
+// RUN: -analyzer-config core.CallAndMessage:ArgPointeeInitializedness=false
\
+// RUN: -analyzer-config core.CallAndMessage:ArgInitializedness=true
// no-pointee-no-diagnostics
@@ -22,3 +29,21 @@ void pointee_uninit(void) {
// checker, as described in the CallAndMessage comments!
// CHECK: <key>issue_hash_content_of_line_in_context</key>
// CHECK-SAME: <string>97a74322d64dca40aa57303842c745a1</string>
+
+typedef struct {
+ int i :2;
+ int :30; // unnamed bit-field
+} B;
+
+extern void consume_B(B);
+
+void bitfield_B_init(void) {
+ B b1;
+ b1.i = 1; // b1 is initialized
+ consume_B(b1);
+}
+
+void bitfield_B_uninit(void) {
+ B b2;
+ consume_B(b2); // arg-init-warning{{Passed-by-value struct argument contains
uninitialized data (e.g., field: 'i') [core.CallAndMessage]}}
+}
\ No newline at end of file
diff --git a/clang/test/Analysis/call-and-message.cpp
b/clang/test/Analysis/call-and-message.cpp
index 25ae23833478b..1e76973f49e13 100644
--- a/clang/test/Analysis/call-and-message.cpp
+++ b/clang/test/Analysis/call-and-message.cpp
@@ -169,4 +169,20 @@ void record_uninit() {
// CHECK-SAME: <string>a46bb5c1ee44d4611ffeb13f7f499605</string>
// CHECK: <key>issue_hash_content_of_line_in_context</key>
// CHECK-SAME: <string>e0e0d30ea5a7b2e3a71e1931fa0768a5</string>
+
+struct B{
+ int i :2;
+ int :30; // unnamed bit-field
+};
+
+void bitfield_B_init(void) {
+ B b1;
+ b1.i = 1; // b1 is initialized
+ consume(b1);
+}
+
+void bitfield_B_uninit(void) {
+ B b2;
+ consume(b2); // arg-init-warning{{Passed-by-value struct argument contains
uninitialized data (e.g., field: 'i') [core.CallAndMessage]}}
+}
} // namespace uninit_arg
``````````
</details>
https://github.com/llvm/llvm-project/pull/145066
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