pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Alexander Lakhin <exclusion@gmail.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Undefined behavior detected by new clang's ubsan
Date: Tue, 20 Jan 2026 07:00:00 +0200
Message-ID: <777bd201-6e3a-4da0-a922-4ea9de46a3ee@gmail.com> (raw )
Hello hackers.
When trying to run `make check` for a build made by clang-21 with
sanitizers enabled:
CFLAGS="-Og -fsanitize=address -fsanitize=undefined -fno-sanitize-recover -fno-sanitize=function"
LDFLAGS="-static-libsan" ...
I hit into:
../../src/include/lib/sort_template.h:314:15: runtime error: applying non-zero offset 8 to null pointer
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../src/include/lib/sort_template.h:314:15
I could workaround that with:
inline patch 1: src/include/lib/sort_template.h (+3/-0 lines) download inline-1.patch --- a/src/include/lib/sort_template.h
+++ b/src/include/lib/sort_template.h
@@ -307,6 +307,9 @@ ST_SORT(ST_ELEMENT_TYPE * data, size_t n
int r,
presorted;
+if (!data && n == 0)
+ return;
+
loop:
https://releases.llvm.org/20.1.0/tools/clang/docs/ReleaseNotes.html#sanitizers
Changed -fsanitize=pointer-overflow to no longer report NULL + 0 as undefined behavior in C, in line with N3322, and
matching the previous behavior for C++. NULL + non_zero continues to be reported as undefined behavior.
Best regards,
Alexander
Patches and attachments: download all (2 files, .tar.gz)
fixes-for-new-clang-sanitizers.patch (text/x-patch, 2.1K) download
diff --git a/contrib/pg_trgm/trgm_gist.c b/contrib/pg_trgm/trgm_gist.c
index 5c7deb103a6..3a10c8380b7 100644
--- a/contrib/pg_trgm/trgm_gist.c
+++ b/contrib/pg_trgm/trgm_gist.c
@@ -699,7 +699,7 @@ gtrgm_penalty(PG_FUNCTION_ARGS)
if (ISARRKEY(newval))
{
char *cache = (char *) fcinfo->flinfo->fn_extra;
- TRGM *cachedVal = (TRGM *) (cache + MAXALIGN(siglen));
+ TRGM *cachedVal = cache ? ((TRGM *) (cache + MAXALIGN(siglen))) : NULL;
Size newvalsize = VARSIZE(newval);
BITVECP sign;
diff --git a/src/backend/access/heap/heaptoast.c b/src/backend/access/heap/heaptoast.c
index e28fe47a449..13884c26213 100644
--- a/src/backend/access/heap/heaptoast.c
+++ b/src/backend/access/heap/heaptoast.c
@@ -768,7 +768,7 @@ heap_fetch_toast_slice(Relation toastrel, Oid valueid, int32 attrsize,
chcpyend = (sliceoffset + slicelength - 1) % TOAST_MAX_CHUNK_SIZE;
memcpy(VARDATA(result) +
- (curchunk * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt,
+ (int)(curchunk * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt,
chunkdata + chcpystrt,
(chcpyend - chcpystrt) + 1);
diff --git a/src/backend/utils/sort/sharedtuplestore.c b/src/backend/utils/sort/sharedtuplestore.c
index 8f35a255263..40f9a4606a5 100644
--- a/src/backend/utils/sort/sharedtuplestore.c
+++ b/src/backend/utils/sort/sharedtuplestore.c
@@ -323,7 +323,7 @@ sts_puttuple(SharedTuplestoreAccessor *accessor, void *meta_data,
/* Do we have space? */
size = accessor->sts->meta_data_size + tuple->t_len;
- if (accessor->write_pointer + size > accessor->write_end)
+ if ((accessor->write_pointer == NULL && accessor->write_end == NULL && size > 0) || (accessor->write_pointer + size > accessor->write_end))
{
if (accessor->write_chunk == NULL)
{
diff --git a/src/include/lib/sort_template.h b/src/include/lib/sort_template.h
index e02aa73cd4d..71353cdbd72 100644
--- a/src/include/lib/sort_template.h
+++ b/src/include/lib/sort_template.h
@@ -307,6 +307,9 @@ ST_SORT(ST_ELEMENT_TYPE * data, size_t n
int r,
presorted;
+if (!data && n == 0)
+ return;
+
loop:
DO_CHECK_FOR_INTERRUPTS();
if (n < 7)
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Message-ID: <777bd201-6e3a-4da0-a922-4ea9de46a3ee@gmail.com>
Permalink: ../777bd201-6e3a-4da0-a922-4ea9de46a3ee@gmail.com/
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To: pgsql-hackers@postgresql.org
Cc: exclusion@gmail.com
Subject: Re: Undefined behavior detected by new clang's ubsan
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