replica
/
hanchenye-llvm-project
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Fix bad CFG construction bug when handling C++ 'try' statements. 

This code assigned the last created CFGBlock* to the variable 'Block',
which is a scratch variable which is null'ed out after a block is
completed.  By assigning the last created block to 'Block', we start
editing a completed block, inserting CFGStmts that should be in
another block.  This was the case with 'try'.  The test case that
showed this had a while loop inside a 'try', and the logic before
the while loop was being included as part of the "condition block"
for the loop.  This showed up as a bogus dead store, but could
have lots of implications.

Turns out this bug was replicated a few times within CFG.cpp, so
I went and fixed up those as well.

llvm-svn: 167788
This commit is contained in:
Ted Kremenek 2012-11-13 00:12:13 +00:00
parent c94c3bb5d0
commit e6ee671e16
2 changed files with 37 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
clang/lib/Analysis/CFG.cpp
View File

@ -1648,8 +1648,10 @@ CFGBlock *CFGBuilder::VisitDeclSubExpr(DeclStmt *DS) {
// If the type of VD is a VLA, then we must process its size expressions.
for (const VariableArrayType* VA = FindVA(VD->getType().getTypePtr());
VA != 0; VA = FindVA(VA->getElementType().getTypePtr()))
Block = addStmt(VA->getSizeExpr());
VA != 0; VA = FindVA(VA->getElementType().getTypePtr())) {
if (CFGBlock *newBlock = addStmt(VA->getSizeExpr()))
LastBlock = newBlock;
}
// Remove variable from local scope.
if (ScopePos && VD == *ScopePos)
@ -1767,7 +1769,7 @@ CFGBlock *CFGBuilder::VisitIfStmt(IfStmt *I) {
// Add the condition as the last statement in the new block. This may create
// new blocks as the condition may contain control-flow. Any newly created
// blocks will be pointed to be "Block".
Block = addStmt(I->getCond());
CFGBlock *LastBlock = addStmt(I->getCond());
// Finally, if the IfStmt contains a condition variable, add both the IfStmt
// and the condition variable initialization to the CFG.
@ -1775,11 +1777,11 @@ CFGBlock *CFGBuilder::VisitIfStmt(IfStmt *I) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, I->getConditionVariableDeclStmt());
addStmt(Init);
LastBlock = addStmt(Init);
}
}
return Block;
return LastBlock;
}
@ -2611,7 +2613,7 @@ CFGBlock *CFGBuilder::VisitSwitchStmt(SwitchStmt *Terminator) {
// Add the terminator and condition in the switch block.
SwitchTerminatedBlock->setTerminator(Terminator);
Block = SwitchTerminatedBlock;
Block = addStmt(Terminator->getCond());
CFGBlock *LastBlock = addStmt(Terminator->getCond());
// Finally, if the SwitchStmt contains a condition variable, add both the
// SwitchStmt and the condition variable initialization to the CFG.
@ -2619,11 +2621,11 @@ CFGBlock *CFGBuilder::VisitSwitchStmt(SwitchStmt *Terminator) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, Terminator->getConditionVariableDeclStmt());
addStmt(Init);
LastBlock = addStmt(Init);
}
}
return Block;
return LastBlock;
}
static bool shouldAddCase(bool &switchExclusivelyCovered,
@ -2807,8 +2809,7 @@ CFGBlock *CFGBuilder::VisitCXXTryStmt(CXXTryStmt *Terminator) {
assert(Terminator->getTryBlock() && "try must contain a non-NULL body");
Block = NULL;
Block = addStmt(Terminator->getTryBlock());
return Block;
return addStmt(Terminator->getTryBlock());
}
CFGBlock *CFGBuilder::VisitCXXCatchStmt(CXXCatchStmt *CS) {
@ -2949,15 +2950,15 @@ CFGBlock *CFGBuilder::VisitCXXForRangeStmt(CXXForRangeStmt *S) {
addLocalScopeAndDtors(S->getLoopVarStmt());
// Populate a new block to contain the loop body and loop variable.
Block = addStmt(S->getBody());
addStmt(S->getBody());
if (badCFG)
return 0;
Block = addStmt(S->getLoopVarStmt());
CFGBlock *LoopVarStmtBlock = addStmt(S->getLoopVarStmt());
if (badCFG)
return 0;
// This new body block is a successor to our condition block.
addSuccessor(ConditionBlock, KnownVal.isFalse() ? 0 : Block);
addSuccessor(ConditionBlock, KnownVal.isFalse() ? 0 : LoopVarStmtBlock);
}
// Link up the condition block with the code that follows the loop (the

23
clang/test/Analysis/dead-stores.cpp
View File

@ -126,3 +126,26 @@ int test_5() {
return 1;
}
int test_6_aux(unsigned x);
void test_6() {
unsigned currDestLen = 0; // no-warning
try {
while (test_6_aux(currDestLen)) {
currDestLen += 2; // no-warning
}
}
catch (void *) {}
}
void test_6b() {
unsigned currDestLen = 0; // no-warning
try {
while (test_6_aux(currDestLen)) {
currDestLen += 2; // expected-warning {{Value stored to 'currDestLen' is never read}}
break;
}
}
catch (void *) {}
}