VMD-L Mailing List

From: Axel Kohlmeyer (akohlmey_at_cmm.chem.upenn.edu)
Date: Sat Apr 19 2008 - 09:21:04 CDT

On Sat, 19 Apr 2008, Cojocaru,Vlad wrote:

VC> Dear VMD users,

dear vlad,

first off, it would make your mail much more readable for many
people, if you restrict it to plain ASCII characters...

VC> I am building MD from source (CVS) on a LINUXAMD64 (SuSE linux, gcc
VC> 4.2). During the plugin build I get a lot of warning messages. Some
VC> examples are below. The build seems ok inspite of these warnings. My
VC> question is: Shall I worry about these warnings .. or I can go on

warnings always should be taken seriously. the default VMD builds,
however are done at a high warning level, most of the resulting
warnings are rather harmless. with few exceptions they _do_ indicate
not fully standard conforming code or sloppily written code, so
the could should be corrected at some point. but you are obviously
building the plugins and most of that code is contributed, so it
is on average in a worse shape than the main part of VMD.

for most warnings it is rather obvious what to do to get rid of them.
feel free to do it and send in a patch so that everyone benefits from it.

VC> with the build ?

[...]
VC> src/msmsplugin.C:201: warning: dereferencing type-punned pointer will break strict-aliasing rules

this is the only one that may indicate a more serious problem.
recent gcc compilers assume full compliance of the code with ANSI-C
aliasing rules, but compiler has found a region where this seems
not to be the case. this may result in the compiler miscompiling
this plugin and can be alleviated by either fixing the code or
compiling it with -fno-strict-aliasing which will relax the aliasing
constraints at the expense of skipping some possible optimizations.

cheers,
    axel.

VC> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey_at_cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.