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When I use the following minimal code in an c++ ConsoleApp in VS2019, I get two warnings, which are completely opposite.
int main()
{
unsigned char op1 = 0x1;
unsigned char op2 = 0x3;
unsigned char result1 = op1 | op2;
unsigned char result2 = op1 || op2;
}
The warning at unsigned char result1 = op1 | op2; is
lnt-logical-bitwise-mismatch Using bitwise '|' when logical '||' was probably intended.
The warning at unsigned char result2 = op1 || op2; is
lnt-logical-bitwise-mismatch Using logical '||' when bitwise '|' was probably intended.
This is a little bit curious.
My intention was to use the bitwise operator. How could I change the line unsigned char result1 = op1 | op2;, so that the VS2019 warning goes away?
The warning is not from the compiler, the output is error-free.
Maybe it comes from Resharper c++ module or from VS code analysis.
(Of course I could ignore that warning, but in the original code there are a lot of them, because there a lot of unsigned char bitwise operations).
26
1 Answer
Reset to default
18
lnt-logical-bitwise-mismatch is a Visual Studio linter rule. It tells you that logical operators should only be used with booleans:
bool op1 = true;
bool op2 = false;
bool result2 = op1 || op2;
and bitwise operatos should only be used with integers, not chars:
unsigned int op1 = 0x1;
unsigned int op2 = 0x3;
unsigned int result2 = op1 | op2;
See https://learn.microsoft.com/en-us/cpp/ide/lnt-logical-bitwise-mismatch?view=msvc-170 for more details
If you don’t want this warning, you can configure the linter in "Options" -> "Text Editor" -> "C/C++" -> "Code Style" -> "Linter": https://learn.microsoft.com/en-us/cpp/ide/cpp-linter-overview?view=msvc-170#configure-the-linter
I’m not saying that these rules make sense. I’m just answering why you get the squiggles and how you can avoid it. The usefulness of these rules is a different question.
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1
really ? What about?
int *p; float *y; /* ... */; if(p && y) { do_something_();}– 0___________11 hours ago
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@0___________ From the posted link: "Only use logical operators on Boolean values." Disable the linter warning, if you don't want it. It's only a linter rule and a recommendation.
– jabaa11 hours ago
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3
Do I really get downvotes for Microsoft's recommendations or is something wrong with my answer?
– jabaa11 hours ago
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@HolyBlackCat The sentence starts with "It tells you that…" after "
lnt-logical-bitwise-mismatchis a Visual Studio linter rule." It's not my opinion. It's a fact. I'm not here to discuss whether these rules make sense or not. I want to describe when the squiggles appear and how to disable them.– jabaa11 hours ago
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5
"Do I really get downvotes for Microsoft's recommendations" My money on the positive answer. Have an upvote to compensate.
– YSC8 hours ago
It could be because of the type. It could be because the static analyzer thinks none of the expressions make sense. Or it could be a false positive. When and where are you getting these warnings? From the VS IntelliSense? From the compiler? From some third-party analyzer tool? Have you tried to search for the error in the documentation? What does it say?
11 hours ago
Have you read learn.microsoft.com/en-us/cpp/ide/… According to the link
op1 || op2should only be used with booleans andop1 | op2should only be used with integers, not chars11 hours ago
@Rodney Yes, of course, you can do this. But Microsoft doesn't recommend it and its linter gives you a warning.
11 hours ago
@woelfchen42 it isn't a false-positive. It is a true positive of a style rule you disagree with.
11 hours ago
Please don't post code in comments. It's not readable. Edit your question and add it there.
10 hours ago