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Date: Thu, 26 Mar 2020 15:26:12 -0700
From: Fangrui Song <maskray@google.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH v2] powerpc/boot: Delete unneeded .globl _zimage_start
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Cc: Alan Modra <amodra@gmail.com>, Nick Desaulniers <ndesaulniers@google.com>,
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On 2020-03-26, Segher Boessenkool wrote:
>On Wed, Mar 25, 2020 at 09:42:57AM -0700, Fangrui Song wrote:
>> .globl sets the symbol binding to STB_GLOBAL while .weak sets the
>> binding to STB_WEAK. GNU as let .weak override .globl since binutils-gdb
>> 5ca547dc2399a0a5d9f20626d4bf5547c3ccfddd (1996). Clang integrated
>> assembler let the last win but it may error in the future.
>
>GNU AS works for more than just ELF.  The way the assembler language
>is defined, it is not .weak overriding .globl -- instead, .weak sets a
>symbol attribute.  On an existing symbol (but it creates on if there is
>none yet).
>
>Clang is buggy if it does not allow valid (and perfectly normal)
>assembler code like this.

https://sourceware.org/pipermail/binutils/2020-March/110399.html

Alan: "I think it is completely fine for you to make the llvm assembler
error on inconsistent binding, or the last directive win.  Either of
those behaviours is logical and good, but you quite possibly will run
into a need to fix more user assembly.

I am doing some experiments whether making clang integrated assembler
error is feasible.