Re: [Buildroot] [PATCH 1/1] package/libnss fix buildtype

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Ayrton Leyssens <aleyssens@idtech.be>
Cc: "buildroot@buildroot.org" <buildroot@buildroot.org>,
	Gilles Fouarge <gfouarge@idtech.be>
Subject: Re: [Buildroot] [PATCH 1/1] package/libnss fix buildtype
Date: Sat, 17 May 2025 17:18:31 +0200	[thread overview]
Message-ID: <20250517171831.7fddcaa6@windsurf> (raw)
In-Reply-To: <VI1PR06MB8926D3F9BF282F9072C81811AD852@VI1PR06MB8926.eurprd06.prod.outlook.com>

Hello Ayrton,

Thanks for the feedback. More questions/comments below.

On Thu, 24 Apr 2025 06:11:27 +0000
Ayrton Leyssens <aleyssens@idtech.be> wrote:

> The issue presented when we were debugging Certmonger (which I still have to send in correctful).
> Same Cermonger version as a Yocto based reference build.
> So, we looked at the dependencies.
> When checking versions with 'strings libnss.a | grep -i version' we saw version = 3.108 (debug) (while the reference has not).
> Going through the docs of LibNSS, I noticed that the make target of LibNSS is not using the default passed make arguments (like -O2).

Reading the code of nss, I see:

ifdef BUILD_OPT
ifeq (11,$(ALLOW_OPT_CODE_SIZE)$(OPT_CODE_SIZE))
	OPTIMIZER = -Os
else
	OPTIMIZER = -O2
endif

So when BUILD_OPT is 0, no flag is added. And as reported in my
previous e-mail, Buildroot passed CFLAGS -O2 and -g0 are taken into
account.

> When passed no additional arguments as defined (https://firefox-source-docs.mozilla.org/security/nss/build.html ), it is all 0 by default.
> So goes for the BUILD_OPT:
> 0: Build a debug (non-optimized) version of NSS. This is the default.
> 1: Build an optimized (non-debug) version of NSS.
> 
> -O2 disables the production of debug symbols, but the BUILD_OPT var has implications on the source itself.

No -O2 does not disable the production of debug symbols. The -g0 does it.

Could you clarify which implications BUILD_OPT has on the source files?
I went through the nss code base, grepped for BUILD_OPT everywhere, and
couldn't spot how this was having an impact on the source code.

> When in the so called 'debug' build, LibNSS discards all variables / sets them to NULL if not all arguments are passed to some functions.

Could you provide some pointers to the actual code? Also I guess you
meant these are discarded in the optimized build, not the debug build,
right?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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