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[libc] Workaround for gcc complaining about implicit conversions with the ternary ?: operator. #124820

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Jan 28, 2025
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[libc] Workaround for gcc complaining about implicit conversions with the ternary ?: operator. #124820

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[libc] Workaround for gcc complaining about implicit conversions with…
lntue Jan 28, 2025
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Add comment about the root cause.
lntue Jan 28, 2025
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12 changes: 8 additions & 4 deletions libc/src/__support/FPUtil/except_value_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,12 +81,16 @@ template <typename T, size_t N> struct ExceptValues {
StorageType out_bits = values[i].rnd_towardzero_result;
switch (fputil::quick_get_round()) {
case FE_UPWARD:
out_bits += sign ? values[i].rnd_downward_offset
: values[i].rnd_upward_offset;
if (sign)
out_bits += values[i].rnd_downward_offset;
else
out_bits += values[i].rnd_upward_offset;
Comment on lines +84 to +87
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Looking at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101537, I think you can keep the ternary, and instead work around this as such:

Suggested change
if (sign)
out_bits += values[i].rnd_downward_offset;
else
out_bits += values[i].rnd_upward_offset;
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101537
out_bits = out_bits + (sign ? values[i].rnd_downward_offset : values[i].rnd_upward_offset);

ah, but that's not much more readable. Please cite https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101537 in either a comment in the sources and/or the PR description.

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Thanks for finding the root cause of it! I updated the comments.

break;
case FE_DOWNWARD:
out_bits += sign ? values[i].rnd_upward_offset
: values[i].rnd_downward_offset;
if (sign)
out_bits += values[i].rnd_upward_offset;
else
out_bits += values[i].rnd_downward_offset;
break;
case FE_TONEAREST:
out_bits += values[i].rnd_tonearest_offset;
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