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Adjust DatumGetBool macro, this time for sure.

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Commit 23a41573c attempted to fix the DatumGetBool macro to ignore bits
in a Datum that are to the left of the actual bool value.  But it did that
by casting the Datum to bool; and on compilers that use C99 semantics for
bool, that ends up being a whole-word test, not a 1-byte test.  This seems
to be the true explanation for contrib/seg failing in VS2015.  To fix, use
GET_1_BYTE() explicitly.  I think in the previous patch, I'd had some idea
of not having to commit to bool being exactly 1 byte wide, but regardless
of what the compiler's bool is, boolean columns and Datums are certainly
1 byte wide.

The previous fix was (eventually) back-patched into all active versions,
so do likewise with this one.
This commit is contained in:
Tom Lane
2016-04-28 11:50:58 -04:00
parent 4f29edbb16
commit 707c44fe25
1 changed files with 1 additions and 1 deletions
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src/include/postgres.h
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@ -326,7 +326,7 @@ typedef Datum *DatumPtr;
* the left of the width of bool, per comment above. * the left of the width of bool, per comment above.
*/ */
#define DatumGetBool(X) ((bool) (((bool) (X)) != 0)) #define DatumGetBool(X) ((bool) (GET_1_BYTE(X) != 0))
/* /*
* BoolGetDatum * BoolGetDatum