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Date: Fri, 30 Oct 2020 13:54:16 -0700
From: Fangrui Song <i@maskray.me>
To: musl@lists.openwall.com
Message-ID: <20201030205416.l6mx5gtx6pftz2fw@gmail.com>
References: <20201030184402.807422-1-raj.khem@gmail.com>
 <20201030185016.GD534@brightrain.aerifal.cx>
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In-Reply-To: <20201030185016.GD534@brightrain.aerifal.cx>
Subject: Re: [musl] [PATCH] crt: Add .file directive

On 2020-10-30, Rich Felker wrote:
>On Fri, Oct 30, 2020 at 11:44:02AM -0700, Khem Raj wrote:
>> Musl linked binaries come out to be not reproducible because
>> absolute build path is seen in debug info of crti.o and crtn.o
>> This is due to the fact that these objects are built from assembly
>> source files and they are missing .file directive
>> if we add .file <filename>.s in them then debug info encodes this
>> value instead of absolute path in debug_line section

.debug_line is unrelated because there is no .loc directive in these
crti.s and crtn.s files.

Many architectures do not leave non-STT_SECTION STB_LOCAL symbols in
crti.o and crtn.o, so they don't need to be patched (even if the
maintainer agrees to add the workaround in musl, instead of fixing the
toolchain).

>Surely there should be some better way to achieve this with CFLAGS
>instead of duplication across every source file..?
>
>Rich

https://bugs.llvm.org/show_bug.cgi?id=48023 captures the nature of the
problem. You may send a message to binutils@sourceware.org how GCC/gas
should handle this situation.

LLD and gold do not synthesize STT_FILE, hence no such problem.