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| author | Tom Lane | 2015-07-01 22:07:48 +0000 |
|---|---|---|
| committer | Tom Lane | 2015-07-01 22:07:48 +0000 |
| commit | d7c19d68550eb6018e8581a73a351905f4cc435c (patch) | |
| tree | d894366d75e293ae8769d7cfe39b93179f5684d1 | |
| parent | 8217370864c950ea28c7f940442fe48c701461c2 (diff) | |
Make sampler_random_fract() actually obey its API contract.
This function is documented to return a value in the range (0,1),
which is what its predecessor anl_random_fract() did. However, the
new version depends on pg_erand48() which returns a value in [0,1).
The possibility of returning zero creates hazards of division by zero
or trying to compute log(0) at some call sites, and it might well
break third-party modules using anl_random_fract() too. So let's
change it to never return zero. Spotted by Coverity.
Michael Paquier, cosmetically adjusted by me
| -rw-r--r-- | src/backend/utils/misc/sampling.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c index aaf1d6c410..6191f79734 100644 --- a/src/backend/utils/misc/sampling.c +++ b/src/backend/utils/misc/sampling.c @@ -237,7 +237,14 @@ sampler_random_init_state(long seed, SamplerRandomState randstate) double sampler_random_fract(SamplerRandomState randstate) { - return pg_erand48(randstate); + double res; + + /* pg_erand48 returns a value in [0.0 - 1.0), so we must reject 0 */ + do + { + res = pg_erand48(randstate); + } while (res == 0.0); + return res; } |