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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
View File

@@ -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"

11
cpp/ql/test/experimental/query-tests/Best Practices/GuardedFree/GuardedFree.expected
View File

@@ -1,10 +1,5 @@
| test.cpp:5:7:5:7 | x | unnecessary NULL check before call to $@ | test.cpp:6:5:6:8 | call to free | free |
| test.cpp:23:7:23:7 | x | unnecessary NULL check before call to $@ | test.cpp:26:5:26:8 | call to free | free |
| test.cpp:31:7:31:8 | ! ... | unnecessary NULL check before call to $@ | test.cpp:35:3:35:6 | call to free | free |
| test.cpp:31:7:31:24 | ... \|\| ... | unnecessary NULL check before call to $@ | test.cpp:35:3:35:6 | call to free | free |
| test.cpp:31:8:31:8 | x | unnecessary NULL check before call to $@ | test.cpp:35:3:35:6 | call to free | free |
| test.cpp:94:12:94:12 | x | unnecessary NULL check before call to $@ | test.cpp:94:3:94:13 | call to free | free |
| test.cpp:98:7:98:8 | ! ... | unnecessary NULL check before call to $@ | test.cpp:101:3:101:6 | call to free | free |
| test.cpp:98:8:98:8 | x | unnecessary NULL check before call to $@ | test.cpp:101:3:101:6 | call to free | free |
| test.cpp:10:7:10:7 | x | unnecessary NULL check before call to $@ | test.cpp:11:5:11:8 | call to free | free |
| test.cpp:42:7:42:7 | x | unnecessary NULL check before call to $@ | test.cpp:43:5:43:8 | call to free | free |
| test.cpp:49:7:49:7 | x | unnecessary NULL check before call to $@ | test.cpp:50:5:50:8 | call to free | free |
| test.cpp:106:7:106:18 | ... != ... | unnecessary NULL check before call to $@ | test.cpp:107:5:107:8 | call to free | free |
| test.cpp:113:7:113:18 | ... != ... | unnecessary NULL check before call to $@ | test.cpp:114:17:114:20 | call to free | free |

10
cpp/ql/test/experimental/query-tests/Best Practices/GuardedFree/test.cpp
View File

@@ -20,7 +20,7 @@ void test2(int *x) {
}
void test3(int *x, bool b) {
if (x) { // GOOD [FALSE POSITIVE]: x is being accessed in the body of the if
if (x) { // GOOD: x is being accessed in the body of the if
if (b)
*x = 42;
free(x);
@@ -28,7 +28,7 @@ void test3(int *x, bool b) {
}
bool test4(char *x, char *y) {
if (!x || strcmp(x, y)) { // GOOD [FALSE POSITIVE]: x is being accessed in the guard and return value depends on x
if (!x || strcmp(x, y)) { // GOOD: x is being accessed in the guard and return value depends on x
free(x);
return true;
}
@@ -91,11 +91,11 @@ void test10(char *x) {
if (x) free(x);
void test11(char *x) {
TRY_FREE(x) // BAD
TRY_FREE(x) // BAD [NOT DETECTED]
}
bool test12(char *x) {
if (!x) // GOOD [FALSE POSITIVE]: return value depends on x
if (!x) // GOOD: return value depends on x
return false;
free(x);
@@ -110,6 +110,6 @@ void test13(char *x) {
void inspect(char *x);
void test14(char *x) {
if (x != nullptr) // GOOD [FALSE POSITIVE]: x might be accessed in the first operand of the comma operator
if (x != nullptr) // GOOD: x might be accessed in the first operand of the comma operator
inspect(x), free(x);
}