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ValueFlow: don't perform UB when a function returns shifts of/by negative values. Fixes #7814.

This commit is contained in:
Matthias Krüger 2016-11-23 23:26:18 +01:00
parent 8be50fd822
commit 213589ee68
2 changed files with 23 additions and 4 deletions
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17
lib/valueflow.cpp
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@ -2097,10 +2097,19 @@ static void execute(const Token *expr,
*result = result1 / result2; *result = result1 / result2;
else if (expr->str() == "%") else if (expr->str() == "%")
*result = result1 % result2; *result = result1 % result2;
else if (expr->str() == "<<") else if (expr->str() == "<<") {
*result = result1 << result2; if (result2 < 0 || result1 < 0) { // dont perform UB
else if (expr->str() == ">>") *error= true;
*result = result1 >> result2; } else {
*result = result1 << result2;
}
} else if (expr->str() == ">>") {
if (result2 < 0) { // don't perform UB
*error=true;
} else {
*result = result1 >> result2;
}
}
} }
else if (expr->str() == "&&") { else if (expr->str() == "&&") {

10
test/testother.cpp
View File

@ -4626,6 +4626,16 @@ private:
// #6383 - unsigned type // #6383 - unsigned type
check("const int x = (unsigned int)(-1) >> 2;"); check("const int x = (unsigned int)(-1) >> 2;");
ASSERT_EQUALS("", errout.str()); ASSERT_EQUALS("", errout.str());
// #7814 - UB happening in valueflowcode when it tried to compute shifts.
check("int shift1() { return 1 >> -1 ;}\n"
"int shift2() { return 1 << -1 ;}\n"
"int shift3() { return -1 >> 1 ;}\n"
"int shift4() { return -1 << 1 ;}\n");
ASSERT_EQUALS("[test.cpp:1]: (error) Shifting by a negative value is undefined behaviour\n"
"[test.cpp:2]: (error) Shifting by a negative value is undefined behaviour\n"
"[test.cpp:3]: (error) Shifting a negative value is undefined behaviour\n"
"[test.cpp:4]: (error) Shifting a negative value is undefined behaviour\n", errout.str());
} }
void incompleteArrayFill() { void incompleteArrayFill() {