[PATCH] atoi.3: Explain disadvantages of atoi()

From: Arkadiusz Drabczyk <arkadiusz@drabczyk.org>
To: mtk.manpages@gmail.com
Cc: linux-man@vger.kernel.org
Subject: [PATCH] atoi.3: Explain disadvantages of atoi()
Date: Thu, 18 Jun 2020 22:42:41 +0200	[thread overview]
Message-ID: <20200618204241.14476-1-arkadiusz@drabczyk.org> (raw)

I believe new users should be discouraged from using atoi() and that
its disadvantages should be explained.

I added the information that 0 is returned on error - although C
standard and POSIX say that "If the value of the result cannot be
represented, the behavior is undefined." there are some
interpretations that 0 has to be returned
https://stackoverflow.com/questions/38393162/what-can-i-assume-about-the-behaviour-of-atoi-on-error
and this is also what happens in practice with glibc, musl and uClibc.

Signed-off-by: Arkadiusz Drabczyk <arkadiusz@drabczyk.org>
---
 man3/atoi.3 | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/man3/atoi.3 b/man3/atoi.3
index c5894d3..3c6527a 100644
--- a/man3/atoi.3
+++ b/man3/atoi.3
@@ -81,7 +81,18 @@ functions behave the same as
 except that they convert the initial portion of the
 string to their return type of \fIlong\fP or \fIlong long\fP.
 .SH RETURN VALUE
-The converted value.
+The converted value or 0 on error.
+.SH BUGS
+.I errno
+is not set on error so there is no way to distinguish between 0 as an
+error and as the converted value.
+No checks for overflow or underflow are done.
+Only input in decimal base can be converted.
+It's recommended to use
+.BR strtol ()
+and
+.BR strtoul ()
+family of functions in new programs.
 .SH ATTRIBUTES
 For an explanation of the terms used in this section, see
 .BR attributes (7).
-- 
2.9.0

