Fix #1410, Apply fabs to full relative error in UtAssert_DoubleCmpRel#1558
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Fix #1410, Apply fabs to full relative error in UtAssert_DoubleCmpRel#1558sg20180546 wants to merge 1 commit into
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…pRel UtAssert_DoubleCmpRel computed fabs((x) - (y)) / (x), applying fabs only to the numerator. When x is negative the quotient becomes negative, so the comparison (negative <= Ratio) is always true and the assertion passes regardless of how far apart x and y are (false positive). Wrap the entire relative-error expression in fabs so the comparison uses the magnitude of the relative difference: fabs(((x) - (y)) / (x)). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Fix #1410
Describe the contribution
UtAssert_DoubleCmpRelcomputedfabs((x) - (y)) / (x), applyingfabsonly to the numerator. Because the divisor(x)keeps its sign, the relative-error expression becomes negative wheneverx < 0, so the comparison(negative) <= Ratiois always true and the assertion passes no matter how far apartxandyare (false positive).This wraps the entire relative-error expression in
fabsso the comparison uses the magnitude of the relative difference:This matches the fix concurred with by the maintainer in #1410.
Testing performed
x = -1000,y = 1000,Ratio = 1e-10fabs(-1000 - 1000) / (-1000)=-2.0→-2.0 <= 1e-10is true (incorrectly passes)fabs((-1000 - 1000) / (-1000))=2.0→2.0 <= 1e-10is false (correctly fails)x.Expected behavior changes
UtAssert_DoubleCmpRelnow correctly fails when the relative difference exceedsRatiofor negativex, instead of always passing. No change for positivex.System the issue was observed on
Additional context
File changed:
ut_assert/inc/utassert.hPer the issue discussion, this macro is not currently exercised by any active tests, so existing tests are unaffected.
Contributor Info
GitHub: @sg20180546