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I found current clang reports a warning
> warning: Passed-by-value struct argument contains uninitialized data (e.g.,
> field: '') [core.CallAndMessage]
when do static analysis on the following code :
// code piece 1
typedef struct{
unsigned x :3;
unsigned :29;
unsigned y;
}A;
extern void func1(A a);
void func2(){
A a = {0};
func1(a);
}
}
According C or C++ standards, "unnamed bit-fields are skipped during aggregate
initialization." Unnamed bit-fields can not be explicitly initialized, and
taking no explicitly initialization will not cause problems since they would
not be used.
With this patch, no warning will be reported on the above code. And the checker
will still be effective to real warning. e.g. it will report " warning:
Passed-by-value struct argument contains uninitialized data (e.g., field: 'y')
[core.CallAndMessage]" on following code:
typedef struct{
unsigned x :3;
unsigned :29;
unsigned y;
}A;
extern void func1(A a);
void func2(){
A a;
a.x = 0;
func1(a);
}
}
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D146194
Files:
clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
Index: clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
@@ -262,7 +262,9 @@
if (T->getAsStructureType()) {
if (Find(FR))
return true;
- } else {
+ } else if (!I->isUnnamedBitfield()){
+ // unnamed bitfields are skipped during aggregate initialization
+ // Since they are not supposed to be used, warnings should not be
reported
const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
if (V.isUndef())
return true;
Index: clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
@@ -262,7 +262,9 @@
if (T->getAsStructureType()) {
if (Find(FR))
return true;
- } else {
+ } else if (!I->isUnnamedBitfield()){
+ // unnamed bitfields are skipped during aggregate initialization
+ // Since they are not supposed to be used, warnings should not be reported
const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
if (V.isUndef())
return true;
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