Add offnum range checks to suppress compile warnings with UBSAN. Late-model gcc with -fsanitize=undefined enabled issues warnings about uses of PageGetItemId() when it can't prove that the offsetNumber is > 0. The call sites where this happens are checking that the offnum is <= PageGetMaxOffsetNumber(page), so it seems reasonable to add an explicit check that offnum >= 1 too.
While at it, rearrange the code to be less contorted and avoid duplicate checks on PageGetMaxOffsetNumber. Maybe the compiler would optimize away the duplicate logic or maybe not, but the existing coding has little to recommend it anyway. There are multiple instances of this identical coding pattern in heapam.c and heapam_xlog.c. Current gcc only complains about two of them, but I fixed them all in the name of consistency. Potentially this could be back-patched in the name of silencing warnings; but I think enabling UBSAN is mainly something people would do on HEAD, so for now it seems not worth the trouble. Discussion: https://postgr.es/m/[email protected] Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/8191937082a2d4738afc7a232ac08789eea151a3 Modified Files -------------- src/backend/access/heap/heapam.c | 10 +++--- src/backend/access/heap/heapam_xlog.c | 60 +++++++++++++++++------------------ src/backend/access/nbtree/nbtsearch.c | 3 ++ 3 files changed, 38 insertions(+), 35 deletions(-)
