Problem of using malloc() without including stdlib.h

[Phil Race]

Its arguable, whether harmless or not, that each file needs to include it.
Its not unreasonable for an area of the code to have a header file such 
as "awt.h"
that is supposed to be the one that's included by the other files in 
that area of
the code, and which takes care of common includes. jni_util.h is not 
necessarily it.
There isn't a need for every file to include that.
Also many files are 3rd party libs and I don't like editing those as the 
changes
really belong upstream.
So a one size fits all approach might be the answer but I'd want to make 
sure
of that first.

So I'd like to see the list of files that generate actual warnings as 
well as the list
of files that reference malloc but don't include stdlib.h.

We are well aware that returning int as a default is bad in 64 bit .. 
I'd expect
instant death so I'd like to see those actual warnings rather than just the
theoretical ones.

My grep of a current JDK 8 build log for 64 bit Linux shows the only 
malloc warnings
are in hotspot management code. So I am waiting for the proof of the 
real problem

And I can speak for 2d, and if there's 2D files touched I would like to 
see any changes
to those files, and the reasoning discussed on 2d-dev ..

-phil.

On 1/18/2012 8:26 AM, Kelly O'Hair wrote:
> On Jan 18, 2012, at 12:19 AM, Jonathan Lu wrote:
>
>> Hi core-libs-dev,
>>
>> I found that for some native code of OpenJDK code base, malloc() is used without including header file stdlib.h, such as following files,
>> ./src/solaris/native/sun/java2d/opengl/GLXSurfaceData.c
>> ./src/solaris/native/sun/java2d/x11/XRBackendNative.c
>> ....
>>
>> I assume that there's no hacking tricks involved here, right? because this may cause problem for some C compilers, which assumes 'int' as the default return type of a function if it cannot find the function's declaration during compiling. Under such a condition, actual return result of type 'void*' from malloc() will be converted to 'int', which may result in truncated pointers in 64bit platforms. If the application tries to dereference such a broken pointer, error will occur.
>>
>> Indeed I found some indirect includes of stdlib.h, but there're still some I do not see a stdlib.h get included from any of  the direct/indirect included headers. I think in order to fix this problem, two approaches may be considered here,
>> a) add "#include<stdlib.h>" to every missing .c file.
>> b) add "#include<stdlib.h>" to a commonly  referenced header file, such as jni_util.h. but it would not be easy to find such a file for all and creating one is the same as approach a).
>>
> I suggest a)  It should be harmless and is the right thing to do.
>
> It's been a while since I studied the C standard, but I vaguely recall that there was another standard C include file
> that would cause the malloc() prototype declaration to show up.
> Or maybe it wasn't a standard one.  In any case, I think your a) approach is correct and I don't see much a need
> for detailed discussions on this, as long as it builds correctly with no warnings on all platforms. It should be fine and correct.
> That's my 2 cents.
>
> -kto
>
>> But both methods need to change many files, any other ideas about how to fix it more elegantly?
>>
>> Thanks and best regards!
>> - Jonathan
>>