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From: Keith Thompson <Keith.S.Thompson@gmail.com>
Date: Sat, 8 Feb 2020 14:33:47 -0800
Message-ID: <CAAHpriNDNogQw7VR1CSJLqf57q6w0P+8rNV_8Tn7X27i2YTsSA@mail.gmail.com>
Subject: Library man pages don't mention "-D_GNU_SOURCE" (newlib)
To: cygwin@cygwin.com
Cc: Keith Thompson <Keith.S.Thompson@gmail.com>
Content-Type: text/plain; charset="UTF-8"

The exp10 function is a GNU extension, as the man page acknowledges.

The exp10(3) man page (available if you install the "cygwin-doc"
package) doesn't mention that you need to compile with "-D_GNU_SOURCE"
to use it. It seems to be inordinately difficult to find this
information.

The corresponding GNU man page, for example exp10(3) on Ubuntu, says:

SYNOPSIS
       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <math.h>

I suggest adding similar wording to the Cygwin/newlib man pages for
functions that require it.

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