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From: Jan Hubicka <hubicka@kam.mff.cuni.cz>
To: i at maskray dot me <gcc-bugzilla@gcc.gnu.org>
Cc: gcc-bugs@gcc.gnu.org
Subject: Re: [Bug driver/100937] configure: Add
 --enable-default-semantic-interposition
Message-ID: <20211122225448.GA63195@kam.mff.cuni.cz>
References: <bug-100937-4@http.gcc.gnu.org/bugzilla/>
 <bug-100937-4-uxx1KIqN4H@http.gcc.gnu.org/bugzilla/>
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> (The -fno-semantic-interposition thing is probably the biggest performance gap
> between gcc -fpic and clang -fpic.)
Yep, it is often confusing to users (who do not understand what ELF
interposition is) that clang and gcc disagree on default flags here.
Recently -Ofast was extended to imply -fno-semantic-interposition that
will hopefully make more people notice this.

While doing that I have added per-symbol flag about interposition to the
symbol table, so we can also support 

__atttribute__ ((semantic_interposition))

and

__attribute__((no_semantic_interpoition))

if that would be useful for something.