From mboxrd@z Thu Jan  1 00:00:00 1970
From: ron@ronnatalie.com (Ronald Natalie)
Date: Wed, 24 Sep 2014 13:38:14 -0400
Subject: [TUHS] where is ecvt?
In-Reply-To: <CADxT5N6mDEeo=4hERK3AuTGh3+-owQnbpeZSp=bEPJVhjLA02Q@mail.gmail.com>
References: <CADxT5N6mDEeo=4hERK3AuTGh3+-owQnbpeZSp=bEPJVhjLA02Q@mail.gmail.com>
Message-ID: <8843E941-3E0E-4538-A3E4-5D11590794F0@ronnatalie.com>

My guess is that when the libc was built ecvt.s was built into some other file other than ecvt.o and exists in the library under that name.
Ar only reports the file names inserted.   The loader looks at all the symbol tables on the contained files.    Have you tried extracting the files in the archive and running nm on them?