Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #23375

Dereferencing type-punned pointer

Show all headers | View raw

  I keep getting this warning in GCC with the code segment below.

file.c:256 "warning: dereferencing type-punned pointer will break
strict-aliasing rules"

/*****************************************/
char buffer[SIZE];
int length, type;

/* Code to fill buffer */

length = ntohs( *((unsigned short *)buffer) );
type = ntohs( *((unsigned short *)buffer + 1) );

/*****************************************/


I'm trying to take the first two bytes (in network byte order) off the
buffer and put them in the length, followed by the next two bytes into
the type.  GCC complains about the length conversion, but not the type.

What does this warning mean, and should I bother with it?

I don't want to keep checking this forum, so answers by email required. 
Quick responses appreciated.

John

Back to comp.lang.c | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Dereferencing type-punned pointer John May <nospam@nospam.com> - 2012-07-18 20:41 +0000
  Re: Dereferencing type-punned pointer Keith Thompson <kst-u@mib.org> - 2012-07-18 14:14 -0700
    Re: Dereferencing type-punned pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-19 01:33 +0100
  Re: Dereferencing type-punned pointer Keith Thompson <kst-u@mib.org> - 2012-07-18 14:17 -0700
    Re: Dereferencing type-punned pointer Ike Naar <ike@sverige.freeshell.org> - 2012-07-19 06:16 +0000
      Re: Dereferencing type-punned pointer Keith Thompson <kst-u@mib.org> - 2012-07-19 01:35 -0700
        Re: Dereferencing type-punned pointer Ike Naar <ike@sdf.lonestar.org> - 2012-07-19 14:11 +0000
  Re: Dereferencing type-punned pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-19 01:56 +0100
    Re: Dereferencing type-punned pointer Nobody <nobody@nowhere.com> - 2012-07-20 07:40 +0100

csiph-web