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Fix type conversion error in BitFlags Clear #30680

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merged 3 commits into from
Nov 29, 2023
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Merged

Fix type conversion error in BitFlags Clear #30680

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0f203cc
attempt to fix failing CI
fessehaeve Nov 28, 2023
f6b15a7
Merge branch 'master' into pull-request/fix-30679
fessehaeve Nov 28, 2023
d0ff8e2
added test for BitMask Clear function
fessehaeve Nov 28, 2023
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2 changes: 1 addition & 1 deletion src/lib/support/BitFlags.h
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ class BitFlags
*/
BitFlags & Clear(const BitFlags & other)
{
mValue &= ~other.mValue;
mValue &= static_cast<IntegerType>(~static_cast<IntegerType>(other.mValue));
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This is probably not right. The right thing is:

mValue = static_cast<IntegerType>(mValue & ~other.mValue);

or so. Because using &= causes the result of the & (which may have been promoted to a different type) to be assigned to mValue...

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could you provide a test showing this behaviour?

We relied a lot on unit tests to prove that bitflags works for us as expected.

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@bzbarsky-apple bzbarsky-apple Dec 8, 2023 •
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It works correctly. When it compiles. It fails to compile on some compilers, I expect. Depending on optimization settings and the like. Because it triggers -Wconversion warnings due to assigning the int result of & into whatever type mValue is.

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Can we have a compile variant test for this? When this was fixed, we added a unit test that validated we compile.

return *this;
}

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16 changes: 16 additions & 0 deletions src/lib/support/tests/TestBitMask.cpp
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Expand Up @@ -98,10 +98,26 @@ void TestBitMaskInvalid(nlTestSuite * inSuite, void * inContext)
NL_TEST_ASSERT(inSuite, mask.Raw() == 0x1234);
}

void TestClear(nlTestSuite * inSuite, void * inContext)
{
BitMask<TestEnum> mask1;
BitMask<TestEnum> mask2;

mask1.Set(TestEnum::kBit_0);
mask1.Set(TestEnum::kBits_1_2);
mask1.Set(TestEnum::kBits_High8);

mask2.Set(TestEnum::kBits_1_2);
mask1.Clear(mask2);

NL_TEST_ASSERT(inSuite, mask1.Raw() == 0xFF01);
}

const nlTest sTests[] = {
NL_TEST_DEF("BitMask operations", TestBitMaskOperations), //
NL_TEST_DEF("BitFields logic", TestBitFieldLogic), //
NL_TEST_DEF("Invalid operations", TestBitMaskInvalid), //
NL_TEST_DEF("Clear operations", TestClear), //
NL_TEST_SENTINEL() //
};

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