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Merge pull request #17986 from jketema/guarded-free2

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C++: Reduce number of FPs `cpp/guarded-free` and turn `if(x) { free(x) }` cases from FNs to TPs
This commit is contained in:
Jeroen Ketema
2024-11-20 13:58:48 +01:00
committed by GitHub
parent 6a3e34cc4c 84f3e6a0d3
commit b4718792d1
3 changed files with 31 additions and 14 deletions
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24
cpp/ql/src/experimental/Best Practices/GuardedFree.ql
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@@ -18,9 +18,31 @@ class FreeCall extends FunctionCall {
FreeCall() { this.getTarget().hasGlobalName("free") }
}
predicate blockContainsPreprocessorBranches(BasicBlock bb) {
exists(PreprocessorBranch ppb, Location bbLoc, Location ppbLoc |
bbLoc = bb.(Stmt).getLocation() and ppbLoc = ppb.getLocation()
|
bbLoc.getFile() = ppb.getFile() and
bbLoc.getStartLine() < ppbLoc.getStartLine() and
ppbLoc.getEndLine() < bbLoc.getEndLine()
)
}
from GuardCondition gc, FreeCall fc, Variable v, BasicBlock bb
where
gc.ensuresEq(v.getAnAccess(), 0, bb, false) and
fc.getArgument(0) = v.getAnAccess() and
bb = fc.getEnclosingStmt()
bb = fc.getBasicBlock() and
(
// No block statement: if (x) free(x);
bb = fc.getEnclosingStmt()
or
// Block statement with a single nested statement: if (x) { free(x); }
strictcount(bb.(BlockStmt).getAStmt()) = 1
) and
strictcount(BasicBlock bb2 | gc.ensuresEq(_, 0, bb2, _) | bb2) = 1 and
not fc.isInMacroExpansion() and
not blockContainsPreprocessorBranches(bb) and
not (gc instanceof BinaryOperation and not gc instanceof ComparisonOperation) and
not exists(CommaExpr c | c.getAChild*() = fc)
select gc, "unnecessary NULL check before call to $@", fc, "free"