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From: BGB <cr88192@hotmail.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: Android?Why Dalvik?
Date: Mon, 30 May 2011 12:46:33 -0700
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On 5/30/2011 12:25 PM, Joshua Cranmer wrote:
> On 05/30/2011 06:26 AM, BGB wrote:
>> C source code generally doesn't need to change that much between one
>> target and another (after all, most variations in OS and architecture
>> can be trivially handled via #ifdef magic).
>
> I laugh at anyone who thinks this. If you do anything with a GUI, file
> access beyond "open this file and read/write it", networking,
> multithreading, you WILL run into nontrivial portability issues. Heck,
> even porting 32-bit code to a 64-bit target of an otherwise identical
> system is often nontrivial for any decently sized project.
>

as noted, I said "trivially handled via ifdef magic...".


this means, generally:

#ifdef linux
Linux specific stuff...
#endif

#ifdef _WIN32
Windows specific stuff...
#endif

#ifdef MACOSX
Mac specific stuff...
#endif

...

now, the code specific to each OS will only show up on its specific OS.


this includes things like GUI, sound-system interfaces, ...
generally, it is fairly common practice to wrap a lot of this in OS 
specific wrapper code, such that the app is mostly dealing with more 
normalized interfaces internally.

for example, low-level memory allocation:
#ifdef _WIN32
	ptr=VirtualAlloc(...);
#endif
#ifdef linux
	ptr=mmap(...);
#endif
...

but, in general it is far less effort than many people make it out to 
be, and usually only effects a smaller portion of the total code, 
provided the developer(s) know what they are doing.

personally, I have had relatively few issues with 32 and 64 bit 
transitions as well.


yes, and I have done cross-platform apps with network and sound and GUI...