From 1a027e6b7bdf06dc3bfe1e63a2493f13629cf44a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 3 Mar 2022 18:13:24 -0500 Subject: Clean up assorted failures under clang's -fsanitize=undefined checks. Most of these are cases where we could call memcpy() or other libc functions with a NULL pointer and a zero count, which is forbidden by POSIX even though every production version of libc allows it. We've fixed such things before in a piecemeal way, but apparently never made an effort to try to get them all. I don't claim that this patch does so either, but it gets every failure I observe in check-world, using clang 12.0.1 on current RHEL8. numeric.c has a different issue that the sanitizer doesn't like: "ln(-1.0)" will compute log10(0) and then try to assign the resulting -Inf to an integer variable. We don't actually use the result in such a case, so there's no live bug. Back-patch to all supported branches, with the idea that we might start running a buildfarm member that tests this case. This includes back-patching c1132aae3 (Check the size in COPY_POINTER_FIELD), which previously silenced some of these issues in copyfuncs.c. Discussion: https://postgr.es/m/CALNJ-vT9r0DSsAOw9OXVJFxLENoVS_68kJ5x0p44atoYH+H4dg@mail.gmail.com --- src/backend/access/transam/clog.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'src/backend/access/transam/clog.c') diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index 40170b868ba..976aa02acaa 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -296,8 +296,9 @@ TransactionIdSetPageStatus(TransactionId xid, int nsubxids, if (all_xact_same_page && xid == MyPgXact->xid && nsubxids <= THRESHOLD_SUBTRANS_CLOG_OPT && nsubxids == MyPgXact->nxids && - memcmp(subxids, MyProc->subxids.xids, - nsubxids * sizeof(TransactionId)) == 0) + (nsubxids == 0 || + memcmp(subxids, MyProc->subxids.xids, + nsubxids * sizeof(TransactionId)) == 0)) { /* * If we can immediately acquire XactSLRULock, we update the status of -- cgit v1.2.3