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[clang][analysis] Fix flaky clang/test/Analysis/live-stmts.cpp test
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Multiple people reported flaky bot failures tied to clang/test/Analysis/live-stmts.cpp
I tried reproducing the flaky behavior on my Linux x86_64 system, but
the tests appears to be stable in my context.

Only by looking at the failures reported, I could formulate a potential
diagnosis.
The output always looked almost the same, except that the Exprs dumped
per Basic block were shuffled compared to my expectation.
This suggests to me some ordering issue.

If you look at the backing storage of
`blocksEndToLiveness[B].liveExprs`, it uses `llvm::ImmutableSet<const Expr *>`.
That container likely uses the pointer values as keys, thus the runtime
values of the addresses influence the iteration order.

To fix this, before dumping, I sort the expressions by their
"beginLocs". It should be efficient enough for a debug checker, where
there is no performance constraint.

This should hopefully fix the flaky behavior on systems where ASLR works
differently than (my) Linux system.

Hopefully fixes #126619
Hopefully fixes #126804
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@steakhal
steakhal committed Feb 12, 2025
1 parent 324e27e commit 2b0b223
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Showing 2 changed files with 32 additions and 24 deletions.
11 changes: 10 additions & 1 deletion clang/lib/Analysis/LiveVariables.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,9 @@
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/FlowSensitive/DataflowWorklist.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <optional>
Expand Down Expand Up @@ -662,12 +664,19 @@ void LiveVariables::dumpExprLiveness(const SourceManager &M) {
}

void LiveVariablesImpl::dumpExprLiveness(const SourceManager &M) {
auto ByBeginLoc = [&M](const Expr *L, const Expr *R) {
return M.isBeforeInTranslationUnit(L->getBeginLoc(), R->getBeginLoc());
};

// Don't iterate over blockEndsToLiveness directly because it's not sorted.
for (const CFGBlock *B : *analysisContext.getCFG()) {

llvm::errs() << "\n[ B" << B->getBlockID()
<< " (live expressions at block exit) ]\n";
for (const Expr *E : blocksEndToLiveness[B].liveExprs) {
std::vector<const Expr *> LiveExprs;
llvm::append_range(LiveExprs, blocksEndToLiveness[B].liveExprs);
llvm::sort(LiveExprs, ByBeginLoc);
for (const Expr *E : LiveExprs) {
llvm::errs() << "\n";
E->dump();
}
Expand Down
45 changes: 22 additions & 23 deletions clang/test/Analysis/live-stmts.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,3 @@
// Flaky on aarch64: http://llvm.org/PR126619
// UNSUPPORTED: target=aarch64{{.*}}

// RUN: %clang_analyze_cc1 -w -analyzer-checker=debug.DumpLiveExprs %s 2>&1\
// RUN: | FileCheck %s

Expand Down Expand Up @@ -29,34 +26,36 @@ int testThatDumperWorks(int x, int y, int z) {
// CHECK-EMPTY:
// CHECK: [ B2 (live expressions at block exit) ]
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'y' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'z' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: ImplicitCastExpr {{.*}} <IntegralToBoolean>
// CHECK-NEXT: `-ImplicitCastExpr {{.*}} <LValueToRValue>
// CHECK-NEXT: `-DeclRefExpr {{.*}} 'x' 'int'
// CHECK-EMPTY:
// CHECK-EMPTY:
// CHECK: [ B3 (live expressions at block exit) ]
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'y' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'z' 'int'
// CHECK-EMPTY:
// CHECK-EMPTY:
// CHECK: [ B3 (live expressions at block exit) ]
// CHECK-EMPTY:
// CHECK-NEXT: ImplicitCastExpr {{.*}} <IntegralToBoolean>
// CHECK-NEXT: `-ImplicitCastExpr {{.*}} <LValueToRValue>
// CHECK-NEXT: `-DeclRefExpr {{.*}} 'x' 'int'
// CHECK: [ B4 (live expressions at block exit) ]
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'y' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'z' 'int'
// CHECK-EMPTY:
// CHECK-EMPTY:
// CHECK: [ B4 (live expressions at block exit) ]
// CHECK-EMPTY:
// CHECK-NEXT: ImplicitCastExpr {{.*}} <IntegralToBoolean>
// CHECK-NEXT: `-ImplicitCastExpr {{.*}} <LValueToRValue>
// CHECK-NEXT: `-DeclRefExpr {{.*}} 'x' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'y' 'int'
// CHECK-EMPTY:
// CHECK-NEXT: DeclRefExpr {{.*}} 'z' 'int'
// CHECK-EMPTY:
// CHECK-EMPTY:
// CHECK: [ B5 (live expressions at block exit) ]
// CHECK-EMPTY:
Expand Down Expand Up @@ -226,15 +225,15 @@ int logicalOpInTernary(bool b) {
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: BinaryOperator {{.*}} '_Bool' '||'
// CHECK: |-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: | `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK: `-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 0
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 1
Expand All @@ -245,15 +244,15 @@ int logicalOpInTernary(bool b) {
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: BinaryOperator {{.*}} '_Bool' '||'
// CHECK: |-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: | `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK: `-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 0
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 1
Expand All @@ -264,15 +263,15 @@ int logicalOpInTernary(bool b) {
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: BinaryOperator {{.*}} '_Bool' '||'
// CHECK: |-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: | `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK: `-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 0
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 1
Expand All @@ -283,15 +282,15 @@ int logicalOpInTernary(bool b) {
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: BinaryOperator {{.*}} '_Bool' '||'
// CHECK: |-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: | `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK: `-ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: ImplicitCastExpr {{.*}} '_Bool' <LValueToRValue>
// CHECK: `-DeclRefExpr {{.*}} '_Bool' lvalue ParmVar {{.*}} 'b' '_Bool'
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 0
// CHECK-EMPTY:
// CHECK: IntegerLiteral {{.*}} 'int' 1
Expand Down

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