Re: jsonapi: scary new warnings with LTO enabled

Em qua., 16 de abr. de 2025 às 18:42, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> escreveu:

> I noticed some new warnings from buildfarm member chafer,
> which I'm able to reproduce locally on a Fedora 41 box
> by building with "meson setup build -Db_lto=true":
>
> ninja: Entering directory `build'
> [1515/2472] Linking target src/interfaces/libpq/libpq.so.5.18
> In function 'freeJsonLexContext',
> inlined from 'freeJsonLexContext' at ../src/common/jsonapi.c:688:1,
> inlined from 'handle_oauth_sasl_error' at
> ../src/interfaces/libpq/fe-auth-oauth.c:547:2:
> ../src/common/jsonapi.c:723:17: warning: 'free' called on unallocated
> object 'lex' [-Wfree-nonheap-object]
> 723 | FREE(lex);
> | ^
> ../src/interfaces/libpq/fe-auth-oauth.c: In function
> 'handle_oauth_sasl_error':
> ../src/interfaces/libpq/fe-auth-oauth.c:479:24: note: declared here
> 479 | JsonLexContext lex = {0};
> | ^
> [2407/2472] Linking target
> src/test/modules/test_json_parser/test_json_parser_incremental_shlib
> In function 'freeJsonLexContext',
> inlined from 'freeJsonLexContext' at ../src/common/jsonapi.c:688:1,
> inlined from 'main' at
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c:198:2:
> ../src/common/jsonapi.c:723:17: warning: 'free' called on unallocated
> object 'lex' [-Wfree-nonheap-object]
> 723 | FREE(lex);
> | ^
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c: In
> function 'main':
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c:87:24:
> note: declared here
> 87 | JsonLexContext lex;
> | ^
> [2426/2472] Linking target
> src/test/modules/test_json_parser/test_json_parser_incremental
> In function 'pg_free',
> inlined from 'pfree' at ../src/common/fe_memutils.c:135:2,
> inlined from 'freeJsonLexContext' at ../src/common/jsonapi.c:723:3,
> inlined from 'freeJsonLexContext' at ../src/common/jsonapi.c:688:1,
> inlined from 'main' at
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c:198:2:
> ../src/common/fe_memutils.c:107:9: warning: 'free' called on unallocated
> object 'lex' [-Wfree-nonheap-object]
> 107 | free(ptr);
> | ^
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c: In
> function 'main':
> ../src/test/modules/test_json_parser/test_json_parser_incremental.c:87:24:
> note: declared here
> 87 | JsonLexContext lex;
> | ^
>
> AFAICT there is no actual bug here: the FREE() call is reached only if
> the JSONLEX_FREE_STRUCT flag is set, which it should not be for these
> call sites.

See the function *makeJsonLexContextCstringLen* (line 400)
The JSONLEX_FREE_STRUCT is enabled, no?

fe-auth-oauth.c (line 507)
makeJsonLexContextCstringLen(&lex, msg, msglen, PG_UTF8, true);

Worst, on a second call, with lex not NULL, the flags is reseted
and the struct will no longer be released?

best regards,
Ranier Vilela