[lttng-dev] Babeltrace for MINGW32

[Ikaheimonen, JP]

Thank you Mathieu for your prompt answer,
I will keep these guidelines in mind.

JP Ikaheimonen
Mentor Graphics Embedded Systems Division
Nucleus(r) | Linux(r) | Android(tm) | Services | UI | Multi-OS

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-----Original Message-----
From: Mathieu Desnoyers [mailto:mathieu.desnoyers at efficios.com] 
Sent: 28. helmikuuta 2013 14:56
To: Ikaheimonen, JP
Cc: lttng-dev at lists.lttng.org
Subject: Re: [lttng-dev] Babeltrace for MINGW32

* Mathieu Desnoyers (mathieu.desnoyers at efficios.com) wrote:
> * Ikaheimonen, JP (jp_ikaheimonen at mentor.com) wrote:
> > Hi,
> > 
> > I am interested in building a statically linked 32-bit Windows 
> > executable of babeltrace.  For that purpose, I have taken a shot at 
> > building babeltrace 1.0.3 with MinGW.  As for now, I've managed to 
> > build the main executable, which is all I'm interested about.
> > Babeltrace-log and the test suite will not build right now.
> > 
> > MinGW is missing many library functions that babeltrace uses. I have 
> > written replacements for many of these. The replacement functions 
> > are not fully compliant with the original specifications, but they 
> > work well enough under babeltrace. This required some changed in the 
> > configure.ac file as well, so that my versions of uuid, fmemopen and 
> > open_memstream are correctly detected.
> 
> Hopefully you use babeltrace master formats/ctf/memstream.h for 
> fmemopen and open_memstream, and include/babeltrace/uuid.h.
> 
> > 
> > Occasionally, I have had to make changes to the babeltrace source 
> > code. As an example, MinGW cannot use directory file handles in any 
> > meaningful way, so functions such as openat() and dirfd() are out of 
> > the question. I have circumvented these problems by using open() 
> > instead of openat(). Also, MinGW seems to have a problem using 
> > pthread mutexes in a statically linked executable, so I'm just not 
> > using the float_mutex at all. I do not think that's a problem for 
> > me, as I'm using babeltrace as a single-threaded executable instead of a library.

By the way, it would be good to find a way to get this mutex to work.
It's the only mutex needed to make babeltrace a fully reentrant library, and I'd like to keep it that way. In the long run, it's probably easier to fix that to document and explain the limitation,

Thanks,

Mathieu

> > 
> > I have flagged all source code changes with #ifdef __MINGW32__ .
> > 
> > Would these changes be of interest to the babeltrace community? How 
> > likely would they be accepted into the main sources?
> 
> In pretty much all lttng-related user-space projects, we have a 
> "compat/" directory that contains compatibility wrappers (for 
> kernel-related projects like lttng-modules, we call it "wrapper").
> Please have a look at lttng-tools src/common/compat for examples. 
> Adding one to babeltrace seems like the way to go.
> 
> We already have wrappers like this under formats/ctf/memstream.h and 
> include/babeltrace/uuid.h in the babeltrace project. As we add more 
> compatibility layer headers, it would be good to move them all into 
> the same location.
> 
> This allows us to move the complexity of supporting multiple 
> environments into localized files. Therefore, as a general rule, I 
> don't want to see any #ifdef __MINGW32__ anywhere but within compat/ 
> files. If you need to change behavior specifically for mingw (or any 
> architecture), you will need to create a compatibility layer that 
> hides this from the generic code under a simple function call (or 
> static inline).
> 
> Thanks,
> 
> Mathieu
> 
> > 
> > Thank you,
> > 
> > JP Ikaheimonen
> > Mentor Graphics Embedded Systems Division
> > Nucleus(r) | Linux(r) | Android(tm) | Services | UI | Multi-OS
> > 
> > Android is a trademark of Google Inc. Use of this trademark is subject to Google Permissions.
> > Linux is the registered trademark of Linus Torvalds in the U.S. and other countries.
> > 
> > 
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> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> 
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--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com