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From: Matheus Alcantara <[email protected]>
To: Fujii Masao <[email protected]>
To: Ranier Vilela <[email protected]>
Cc: Pg Hackers <[email protected]>
Subject: Re: Avoid resource leak (contrib/postgres_fdw/connection.c)
Date: Wed, 18 Mar 2026 14:42:35 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAHGQGwG2iC2LeizHiCezb-D=G6RE-ACXbFVfeAtzXwjnMTveGA@mail.gmail.com>
References: <CAEudQAprLegxufoi93JuFVkCDmjT5wtGhu3gxT-E1Fg+1DGrag@mail.gmail.com>
	<CAHGQGwG2iC2LeizHiCezb-D=G6RE-ACXbFVfeAtzXwjnMTveGA@mail.gmail.com>

On 16/03/26 20:07, Fujii Masao wrote:
> On Mon, Mar 16, 2026 at 8:46 PM Ranier Vilela <[email protected]> wrote:
>>
>> Hi.
>>
>> Per Coverity.
>>
>> CID 1645716: (#1 of 1): Resource leak (RESOURCE_LEAK)
>> 8. leaked_storage: Variable str going out of scope leaks the storage str.data points to.
>>
>> The function *postgres_fdw_connection* leaks the contents of
>> var str.data
>> Once that function *cstring_to_text* palloc the contents
>> must be necessary to free the var str.data.
> 
> It seems that postgres_fdw_connection() is expected to be called by
> ForeignServerConnectionString() via OidFunctionCall3(),
> and to allocate memory (including str.data) in the FDWConnectionContext
> memory context created by ForeignServerConnectionString().
> 
> After calling postgres_fdw_connection(), ForeignServerConnectionString()
> deletes FDWConnectionContext. So it seems to me that any memory
> allocated in that context, including str.data, would not leak. No?
> 

Yeah, this sounds correct, but I'm wondering if the current pfree 
calls on postgres_fdw_connection() is needed?

My previous review was assuming that any allocated memory on 
postgres_fdw_connection() should be free at the end because of these 
calls, but ForeignServerConnectionString() already assume that this 
function leak memory:
	/*
	 * GetForeignServer, GetForeignDataWrapper, and the connection function
	 * itself all leak memory into CurrentMemoryContext. Switch to a temporary
	 * context for easy cleanup.
	 */
	tempContext = AllocSetContextCreate(CurrentMemoryContext,
										"FDWConnectionContext",
										ALLOCSET_SMALL_SIZES);

--
Matheus Alcantara
EDB: https://www.enterprisedb.com

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