Re: Ubsan complaint on kestrel

Hi,

On 2025-03-03 15:00:43 -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > I just upgraded buildfarm animal kestrel (a buildfarm animal running with
> > ubsan) to a newer version of clang. Unfortunately this causes it to fail.
> > ...
> > Tom, do you see any reason to not instead do the typecase inside
> > string_compare()?
>
> No. Have at it.

Ugh. That change is obviously easy enough.

But after fixing that the next complaint is:

----------------------------------- stderr -----------------------------------
../../../../../home/andres/src/postgresql/src/include/lib/sort_template.h:316:28: runtime error: call to function list_oid_cmp through pointer to incorrect function type 'int (*)(const void *, const void *)'
/srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/nodes/list.c:1704: note: list_oid_cmp defined here
#0 0x5646f45c753f in pg_qsort /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/include/lib/sort_template.h:316:28
#1 0x5646f32df4e0 in list_sort /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/nodes/list.c:1684:3
#2 0x5646f43c6ce9 in RelationGetIndexList /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/utils/cache/relcache.c:4857:2
#3 0x5646f2fe0159 in ExecOpenIndices /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/executor/execIndexing.c:179:17
#4 0x5646f2b51c96 in CatalogOpenIndexes /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/catalog/indexing.c:52:2
#5 0x5646f2b530c8 in CatalogTupleUpdate /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/catalog/indexing.c:320:13
#6 0x5646f2af4e6e in ExecGrant_Relation /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/catalog/aclchk.c:1990:4
#7 0x5646f2ae7adf in ExecGrantStmt_oids /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/catalog/aclchk.c:608:4
#8 0x5646f2ae5aab in ExecuteGrantStmt /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/catalog/aclchk.c:593:2
#9 0x5646f3c19883 in ProcessUtilitySlow /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:1812:5
#10 0x5646f3c1133c in standard_ProcessUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:969:6
#11 0x5646f3c0efc6 in ProcessUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:523:3
#12 0x5646f3c0ce77 in PortalRunUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:1184:2
#13 0x5646f3c0a250 in PortalRunMulti /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:1348:5
#14 0x5646f3c079fc in PortalRun /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:819:5
#15 0x5646f3bf8f5d in exec_simple_query /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:1272:10
#16 0x5646f3bf7276 in PostgresMain /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:4693:7
#17 0x5646f3bf627b in PostgresSingleUserMain /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:4132:2
#18 0x5646f32cac35 in main /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/main/main.c:226:4
#19 0x7f5d3c56bca7 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#20 0x7f5d3c56bd64 in __libc_start_main csu/../csu/libc-start.c:360:3
#21 0x5646f25c7580 in _start (/srv/dev/build/postgres/m-dev-assert-clang-sanitizer/tmp_install/srv/dev/install/postgres/m-dev-assert-clang-sanitizer/bin/postgres+0x21c7580) (BuildId: 3af3be5da960a221ffc2e2805234af46b9ef1b5a)

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../../../../home/andres/src/postgresql/src/include/lib/sort_template.h:316:28
Aborted (core dumped)
child process exited with exit code 134
initdb: data directory "/srv/dev/build/postgres/m-dev-assert-clang-sanitizer/tmp_install/initdb-template" not removed at user's request

Fixing all list comparators would be rather painful. So I fixed it by using
qsort_arg() and a wrapper function.

Which is followed by:

../../../../../home/andres/src/postgresql/src/backend/nodes/nodeFuncs.c:2712:6: runtime error: call to function assign_query_collations_walker through pointer to incorrect function type 'bool (*)(struct Node *, void *)'
/srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/parser/parse_collate.c:127: note: assign_query_collations_walker defined here
#0 0x55c8ee0ffbd8 in query_tree_walker_impl /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/nodes/nodeFuncs.c:2712:6
#1 0x55c8ee4d5df1 in assign_query_collations /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/parser/parse_collate.c:109:9
#2 0x55c8ee47aa58 in transformReturnStmt /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/parser/analyze.c:2499:2
#3 0x55c8ee4683f4 in transformStmt /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/parser/analyze.c:465:13
#4 0x55c8edb2b54f in interpret_AS_clause /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/commands/functioncmds.c:969:8
#5 0x55c8edb26977 in CreateFunction /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/commands/functioncmds.c:1237:2
#6 0x55c8eea1900f in ProcessUtilitySlow /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:1658:15
#7 0x55c8eea11b21 in standard_ProcessUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:1070:4
#8 0x55c8eea0f046 in ProcessUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/utility.c:523:3
#9 0x55c8eea0cef7 in PortalRunUtility /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:1184:2
#10 0x55c8eea0a2d0 in PortalRunMulti /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:1348:5
#11 0x55c8eea07a7c in PortalRun /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/pquery.c:819:5
#12 0x55c8ee9f8fdd in exec_simple_query /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:1272:10
#13 0x55c8ee9f72f6 in PostgresMain /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:4693:7
#14 0x55c8ee9f62fb in PostgresSingleUserMain /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/tcop/postgres.c:4132:2
#15 0x55c8ee0cac35 in main /srv/dev/build/postgres/m-dev-assert-clang-sanitizer/../../../../../home/andres/src/postgresql/src/backend/main/main.c:226:4
#16 0x7f6c4116bca7 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#17 0x7f6c4116bd64 in __libc_start_main csu/../csu/libc-start.c:360:3
#18 0x55c8ed3c7580 in _start (/srv/dev/build/postgres/m-dev-assert-clang-sanitizer/tmp_install/srv/dev/install/postgres/m-dev-assert-clang-sanitizer/bin/postgres+0x21c7580) (BuildId: 8d0a126082525373680eb87eaaa6e91cb98d57a6)

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../../../../home/andres/src/postgresql/src/backend/nodes/nodeFuncs.c:2712:6

And I suspect that if I fixed that one there'd be heaps more.

So I suspect we'll need to disable this sub-sanitizer for now.

On https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html I found
-fsanitize=function, which also can be used as -fno-sanitize=function:
> -fsanitize=function: Indirect call of a function through a function pointer of the wrong type.

With that I can get past this issue.

I wish the sanitizer treated mismatches of void * arguments against a "real
type" different from other mismatches, but ...

Greetings,

Andres Freund