On Tue, May 24, 2022 at 11:17:39PM -0700, Andres Freund wrote:
> On 2022-05-24 11:41:49 -0700, Nathan Bossart wrote:
>> I would actually ERROR on this so that we aren't relying on
>> --enable-cassert builds to catch it.
>
> How about adding pg_nonnull(...) (ending up as __attribute__((nonnull(...))?
> Then code passing NULLs would get compiler warnings? It'd be useful in quite a
> few more places.
I attached an attempt at this for the "name" and "valueAddr" arguments for
the DefineCustomXXXVariable functions. It looked like nonnull was
supported by GCC and Clang, but I haven't looked too closely to see whether
we need version checks as well.
>> That being said, if there's no strong reason to enforce that a short
>> description be provided, then why not adjust ShowAllGUCConfig() to set that
>> column to NULL when short_desc is missing?
>
> There's a bunch more places that'd need to be adjusted, if we go that way. I
> don't really have an opinion on it.
I looked around and didn't see anywhere else obvious that needed adjustment
besides what Michael pointed out (3ac7d024). Am I missing something?
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
>From 3c2503a1794d40c515f53e632952d59317015d02 Mon Sep 17 00:00:00 2001
From: Steve Chavez <st...@supabase.io>
Date: Tue, 24 May 2022 23:46:40 -0500
Subject: [PATCH v3 1/1] Handle a NULL short_desc in ShowAllGUCConfig
Prevent a segfault when using a SHOW ALL, in case a DefineCustomXXXVariable()
was defined with a NULL short_desc.
---
src/backend/utils/misc/guc.c | 16 +++++++++++++---
src/include/c.h | 10 ++++++++++
src/include/utils/guc.h | 10 +++++-----
3 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8e9b71375c..55d41ae7d6 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9780,7 +9780,16 @@ ShowAllGUCConfig(DestReceiver *dest)
isnull[1] = true;
}
- values[2] = PointerGetDatum(cstring_to_text(conf->short_desc));
+ if (conf->short_desc)
+ {
+ values[2] = PointerGetDatum(cstring_to_text(conf->short_desc));
+ isnull[2] = false;
+ }
+ else
+ {
+ values[2] = PointerGetDatum(NULL);
+ isnull[2] = true;
+ }
/* send it to dest */
do_tup_output(tstate, values, isnull);
@@ -9792,7 +9801,8 @@ ShowAllGUCConfig(DestReceiver *dest)
pfree(setting);
pfree(DatumGetPointer(values[1]));
}
- pfree(DatumGetPointer(values[2]));
+ if (conf->short_desc)
+ pfree(DatumGetPointer(values[2]));
}
end_tup_output(tstate);
@@ -10002,7 +10012,7 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
values[3] = _(config_group_names[conf->group]);
/* short_desc */
- values[4] = _(conf->short_desc);
+ values[4] = conf->short_desc != NULL ? _(conf->short_desc) : NULL;
/* extra_desc */
values[5] = conf->long_desc != NULL ? _(conf->long_desc) : NULL;
diff --git a/src/include/c.h b/src/include/c.h
index 4f16e589b3..f253aa930b 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -144,6 +144,16 @@
#define pg_attribute_no_sanitize_alignment()
#endif
+/*
+ * pg_attribute_nonnull means the compiler should warn if the function is called
+ * with the listed arguments set to NULL.
+ */
+#if defined(__clang_major__) || defined(__GNUC__)
+#define pg_attribute_nonnull(...) __attribute__((nonnull(__VA_ARGS__)))
+#else
+#define pg_attribute_nonnull(...)
+#endif
+
/*
* Append PG_USED_FOR_ASSERTS_ONLY to definitions of variables that are only
* used in assert-enabled builds, to avoid compiler warnings about unused
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index efcbad7842..be691c5e9c 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -303,7 +303,7 @@ extern void DefineCustomBoolVariable(const char *name,
int flags,
GucBoolCheckHook check_hook,
GucBoolAssignHook assign_hook,
- GucShowHook show_hook);
+ GucShowHook show_hook) pg_attribute_nonnull(1, 4);
extern void DefineCustomIntVariable(const char *name,
const char *short_desc,
@@ -316,7 +316,7 @@ extern void DefineCustomIntVariable(const char *name,
int flags,
GucIntCheckHook check_hook,
GucIntAssignHook assign_hook,
- GucShowHook show_hook);
+ GucShowHook show_hook) pg_attribute_nonnull(1, 4);
extern void DefineCustomRealVariable(const char *name,
const char *short_desc,
@@ -329,7 +329,7 @@ extern void DefineCustomRealVariable(const char *name,
int flags,
GucRealCheckHook check_hook,
GucRealAssignHook assign_hook,
- GucShowHook show_hook);
+ GucShowHook show_hook) pg_attribute_nonnull(1, 4);
extern void DefineCustomStringVariable(const char *name,
const char *short_desc,
@@ -340,7 +340,7 @@ extern void DefineCustomStringVariable(const char *name,
int flags,
GucStringCheckHook check_hook,
GucStringAssignHook assign_hook,
- GucShowHook show_hook);
+ GucShowHook show_hook) pg_attribute_nonnull(1, 4);
extern void DefineCustomEnumVariable(const char *name,
const char *short_desc,
@@ -352,7 +352,7 @@ extern void DefineCustomEnumVariable(const char *name,
int flags,
GucEnumCheckHook check_hook,
GucEnumAssignHook assign_hook,
- GucShowHook show_hook);
+ GucShowHook show_hook) pg_attribute_nonnull(1, 4);
extern void MarkGUCPrefixReserved(const char *className);
--
2.25.1
