About makefile

Brock Palen brockp at umich.edu
Fri Oct 9 07:33:31 CDT 2009

On Oct 9, 2009, at 7:05 AM, jarunan at ascomp.ch wrote:

> Hello
> After the compilation, is it compulsory to delete .o file?
> Actually, once I found that .o file do not update unless I delete it  
> before recompiling. I might misunderstand. if not, I would like to  
> know some reason behind.

Make only recompiles files where the source file is newer than the  
resulting file (the .o file).  Thus if you have not modified the  
source file for a .o file, it will not be recompiled and will be  
relinked as is.  If you wish to force everything to recompile (maybe  
new compiler options etc)  then you need to delete all your  
old .o .a .so and .mod files.  So they are recreated with the new  

This is a feature of make, that is really helpful, it keeps you from  
having to wait to recompile code that has already been compiled once,  
if it will not change.

Brock Palen
Center for Advanced Computing
brockp at umich.edu

> Thank you
> Jarunan
> -- 
> Jarunan Panyasantisuk
> Development Engineer
> ASCOMP GmbH, Technoparkstr. 1
> CH-8005 Zurich, Switzerland
> Phone : +41 44 445 4072
> Fax   : +41 44 445 4075
> E-mail: jarunan at ascomp.ch
> www.ascomp.ch

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