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Commit65a588b

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Try to fix portability issue in enum renumbering (again).
The hack embodied in commit4ba61a4 no longer works after today's changeto allow DatumGetFloat4/Float4GetDatum to be inlined (commit14cca1b).Probably what's happening is that the faulty compilers are deciding thatthe now-inlined assignment is a no-op and so they're not required toround to float4 width.We had a bunch of similar issues earlier this year in the degree-basedtrig functions, and eventually settled on using volatile intermediatevariables as the least ugly method of forcing recalcitrant compilersto do what the C standard says (cf commit82311bc). Let's see ifthat method works here.Discussion: <4640.1472664476@sss.pgh.pa.us>
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‎src/backend/catalog/pg_enum.c

Lines changed: 14 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -315,28 +315,30 @@ AddEnumLabel(Oid enumTypeOid,
315315
newelemorder=nbr_en->enumsortorder+1;
316316
else
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{
318-
other_nbr_en= (Form_pg_enum)GETSTRUCT(existing[other_nbr_index]);
319-
newelemorder= (nbr_en->enumsortorder+
320-
other_nbr_en->enumsortorder) /2;
321-
322318
/*
323-
*On some machines, newelemorder may be in a register that's
324-
*wider than float4. We need to force it to be rounded to float4
325-
*precision before making the following comparisons, or we'll get
326-
*wrong results. (Such behavior violates the C standard, but
327-
*fixing the compilers is out of our reach.)
319+
*The midpoint value computed here has to be rounded to float4
320+
*precision, else our equality comparisons against the adjacent
321+
*values are meaningless. The most portable way of forcing that
322+
*to happen with non-C-standard-compliant compilers is to store
323+
*it into a volatile variable.
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*/
329-
newelemorder=DatumGetFloat4(Float4GetDatum(newelemorder));
325+
volatilefloat4midpoint;
330326

331-
if (newelemorder==nbr_en->enumsortorder||
332-
newelemorder==other_nbr_en->enumsortorder)
327+
other_nbr_en= (Form_pg_enum)GETSTRUCT(existing[other_nbr_index]);
328+
midpoint= (nbr_en->enumsortorder+
329+
other_nbr_en->enumsortorder) /2;
330+
331+
if (midpoint==nbr_en->enumsortorder||
332+
midpoint==other_nbr_en->enumsortorder)
333333
{
334334
RenumberEnumType(pg_enum,existing,nelems);
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/* Clean up and start over */
336336
pfree(existing);
337337
ReleaseCatCacheList(list);
338338
gotorestart;
339339
}
340+
341+
newelemorder=midpoint;
340342
}
341343
}
342344

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