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C++: Remove arguable FPs re: sizeof/decltype

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This commit is contained in:
Nora Dimitrijević
2022-09-28 20:01:14 +02:00
parent 592bc18a97
commit 6d5df14547
2 changed files with 18 additions and 1 deletions
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10
cpp/ql/src/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation.ql
View File

@@ -11,6 +11,7 @@
import cpp
import semmle.code.cpp.commons.Exclusions
/** Gets the sub-expression of 'e' with the earliest-starting Location */
Expr normalizeExpr(Expr e) {
if exists(e.(Call).getQualifier())
then result = normalizeExpr(e.(Call).getQualifier())
@@ -26,6 +27,12 @@ predicate isInLoopHead(CommaExpr ce) {
ce.getEnclosingStmt() = any(ForStmt f).getInitialization()
}
predicate isInDecltypeOrSizeof(CommaExpr ce) {
ce.getParent*() instanceof SizeofExprOperator
or
ce.getParent*() = any(Decltype d).getExpr()
}
from CommaExpr ce, Expr left, Expr right, Location leftLoc, Location rightLoc
where
ce.fromSource() and
@@ -34,7 +41,8 @@ where
right = normalizeExpr(ce.getRightOperand()) and
leftLoc = left.getLocation() and
rightLoc = right.getLocation() and
not isInLoopHead(ce) and // HACK to reduce FPs in loop heads; assumption: unlikely to be misread due to '(', ')' delimiters
not isInLoopHead(ce) and // <- HACK to reduce FPs in loop heads; assumption: unlikely to be misread due to '(', ')' delimiters
not isInDecltypeOrSizeof(ce) and // <- Removes arguable FPs since, like function calls (and loop heads), these Exprs have clear delimiters.
leftLoc.getEndLine() < rightLoc.getStartLine() and
leftLoc.getStartColumn() > rightLoc.getStartColumn()
select right, "The indentation after the comma may be misleading (for some tab sizes)."

9
cpp/ql/test/query-tests/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation/test.cpp
View File

@@ -77,6 +77,10 @@ int test(int i, int j, int (*foo)(int), int (*bar)(int, int))
j++);
(void)sizeof(x.foo(i++), // GOOD
j++);
using U = decltype(x.foo(i++), // GOOD? Unlikely to be misread
j++);
(void)sizeof(x.foo(i++), // GOOD? Unlikely to be misread
j++);
// Comma in loops
@@ -86,6 +90,11 @@ int test(int i, int j, int (*foo)(int), int (*bar)(int, int))
i = j = i + j;
}
while (i = foo(j++), // GOOD??? Currently ignoring loop heads
i != j && i != 42 && !foo(j)) {
i = j = i + j;
}
for (i = 0, // GOOD? Currently ignoring loop heads.
j = 1;
i + j < 10;