Hi Hackers, The functions in bitmapset.h that return a Bitmapset * either build a new set or recycle their input, so ignoring the return value is always a bug.
Commit c617aea6acd introduced the macro pg_nodiscard, which generates a compiler warning when the result of a function call is ignored. The List functions in pg_list.h have the same requirement, and commit a378ba49a5c added pg_nodiscard to most of them. However, bitmapset.h was never adjusted. The attached patch adds pg_nodiscard to all functions there that return a Bitmapset *. This patch does not make REALLOCATE_BITMAPSETS redundant. REALLOCATE_BITMAPSETS reallocates the set on every modification, so a stale pointer to the old set is likely to be noticed. However, only at runtime and only in builds that enable it. pg_nodiscard catches the simpler case of dropping the return value entirely at compile time. Best regards Jan -- Jan Nidzwetzki PlanetScale Postgres Core Team
From 23681fa646ad2c51c71fa0a2178acf159122e07d Mon Sep 17 00:00:00 2001 From: Jan Nidzwetzki <[email protected]> Date: Tue, 8 Sep 2026 15:15:27 +0200 Subject: [PATCH] Add pg_nodiscard decorations to Bitmapset functions The functions in bitmapset.h that return a Bitmapset * either build a new set or recycle their input, so ignoring the result is always a bug. Decorate these functions with pg_nodiscard so that the compiler catches ignored return values. Same modification as commit a378ba49a5c did for pg_list. --- src/include/nodes/bitmapset.h | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h index 997f8a1cd96..7d8014513dc 100644 --- a/src/include/nodes/bitmapset.h +++ b/src/include/nodes/bitmapset.h @@ -91,16 +91,19 @@ typedef enum * function prototypes in nodes/bitmapset.c */ -extern Bitmapset *bms_copy(const Bitmapset *a); +pg_nodiscard extern Bitmapset *bms_copy(const Bitmapset *a); extern bool bms_equal(const Bitmapset *a, const Bitmapset *b); extern int bms_compare(const Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_make_singleton(int x); +pg_nodiscard extern Bitmapset *bms_make_singleton(int x); extern void bms_free(Bitmapset *a); -extern Bitmapset *bms_union(const Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_intersect(const Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_difference(const Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_offset_members(const Bitmapset *a, int offset); +pg_nodiscard extern Bitmapset *bms_union(const Bitmapset *a, const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_intersect(const Bitmapset *a, + const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_difference(const Bitmapset *a, + const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_offset_members(const Bitmapset *a, + int offset); extern bool bms_is_subset(const Bitmapset *a, const Bitmapset *b); extern BMS_Comparison bms_subset_compare(const Bitmapset *a, const Bitmapset *b); extern bool bms_is_member(int x, const Bitmapset *a); @@ -120,14 +123,15 @@ extern BMS_Membership bms_membership(const Bitmapset *a); /* these routines recycle (modify or free) their non-const inputs: */ -extern Bitmapset *bms_add_member(Bitmapset *a, int x); -extern Bitmapset *bms_del_member(Bitmapset *a, int x); -extern Bitmapset *bms_add_members(Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_replace_members(Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_add_range(Bitmapset *a, int lower, int upper); -extern Bitmapset *bms_int_members(Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_del_members(Bitmapset *a, const Bitmapset *b); -extern Bitmapset *bms_join(Bitmapset *a, Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_add_member(Bitmapset *a, int x); +pg_nodiscard extern Bitmapset *bms_del_member(Bitmapset *a, int x); +pg_nodiscard extern Bitmapset *bms_add_members(Bitmapset *a, const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_replace_members(Bitmapset *a, + const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_add_range(Bitmapset *a, int lower, int upper); +pg_nodiscard extern Bitmapset *bms_int_members(Bitmapset *a, const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_del_members(Bitmapset *a, const Bitmapset *b); +pg_nodiscard extern Bitmapset *bms_join(Bitmapset *a, Bitmapset *b); /* support for iterating through the integer elements of a set: */ extern int bms_next_member(const Bitmapset *a, int prevbit); -- 2.47.3
