Re: Can I create static c callable library?
On Fri, Sep 28, 2018 at 02:08:25PM +, Atila Neves via Digitalmars-d-learn wrote: > On Thursday, 27 September 2018 at 23:53:50 UTC, Steven Schveighoffer wrote: [...] > > Since C initialization functions have no order to them, it's > > possible that some initialization functions in the D runtime are > > using uninitialized pieces of the C runtime > > No, that can't happen. The C runtime is initialised no matter what you > do (unless you write `_start` yourself), _then_ the global > constructors are run. The code I wrote isn't standard C - it's just > that gcc/clang/cl are all also C++ compilers so they chose to extend > the already existing functionality to C. [...] Potentially some C libraries have not yet been initialized, though. I don't know if the druntime init depends on any of them -- it's doubtful, but if it does, it may cause problems depending on which order library ctors are called. T -- In a world without fences, who needs Windows and Gates? -- Christian Surchi
Re: Can I create static c callable library?
On Thursday, 27 September 2018 at 23:53:50 UTC, Steven
Schveighoffer wrote:
On 9/27/18 8:16 AM, Atila Neves wrote:
On Tuesday, 25 September 2018 at 14:13:50 UTC, Jacob Carlborg
wrote:
On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M
Davis wrote:
If you use -betterC, then it's trivial, because your D
program is restricted to extern(C) functions and features
which don't require druntime. It can also be done without
-betterC (and thus with druntime), but it gets to be _way_
more of a pain, because it requires that you manually
initialize druntime - either by forcing whatever is using
your "C" library to call a specific function to initialize
druntime before using any of its normal functions or by
having every function in the library check whether druntime
has been initialized yet and initialize it if it hasn't been
before it does whatever it's supposed to do.
Shouldn't it be possible to use a C initialization function,
i.e. pragma(crt_constructor) to initialize druntime? Then it
only needs to be initialized once and it's not required to
check if it's initialized all the time.
--
/Jacob Carlborg
Even easier, compile this C file and add the resulting object
file to your (now mostly) D static library:
---
extern int rt_init(void);
extern int rt_term(void);
__attribute__((__constructor__)) void dinit(void) {
rt_init();
}
__attribute__((__destructor__)) void dterm(void) {
rt_term();
}
---
The C runtime will initialise the D runtime for you.
I will point out that this is EXACTLY what
pragma(crt_constructor) does.
Really? Huh. You live, you learn. I didn't even know that pragma
existed - it's not listed here at all:
https://dlang.org/spec/pragma.html
And my comments still aren't answered -- I'm not sure whether
this works correctly or not, as we don't test initializing
druntime before C main runs.
It's worked for me in practice.
Since C initialization functions have no order to them, it's
possible that some initialization functions in the D runtime
are using uninitialized pieces of the C runtime
No, that can't happen. The C runtime is initialised no matter
what you do (unless you write `_start` yourself), _then_ the
global constructors are run. The code I wrote isn't standard C -
it's just that gcc/clang/cl are all also C++ compilers so they
chose to extend the already existing functionality to C.
Re: Can I create static c callable library?
On 9/27/18 8:16 AM, Atila Neves wrote:
On Tuesday, 25 September 2018 at 14:13:50 UTC, Jacob Carlborg wrote:
On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis wrote:
If you use -betterC, then it's trivial, because your D program is
restricted to extern(C) functions and features which don't require
druntime. It can also be done without -betterC (and thus with
druntime), but it gets to be _way_ more of a pain, because it
requires that you manually initialize druntime - either by forcing
whatever is using your "C" library to call a specific function to
initialize druntime before using any of its normal functions or by
having every function in the library check whether druntime has been
initialized yet and initialize it if it hasn't been before it does
whatever it's supposed to do.
Shouldn't it be possible to use a C initialization function, i.e.
pragma(crt_constructor) to initialize druntime? Then it only needs to
be initialized once and it's not required to check if it's initialized
all the time.
--
/Jacob Carlborg
Even easier, compile this C file and add the resulting object file to
your (now mostly) D static library:
---
extern int rt_init(void);
extern int rt_term(void);
__attribute__((__constructor__)) void dinit(void) {
rt_init();
}
__attribute__((__destructor__)) void dterm(void) {
rt_term();
}
---
The C runtime will initialise the D runtime for you.
I will point out that this is EXACTLY what pragma(crt_constructor) does.
And my comments still aren't answered -- I'm not sure whether this works
correctly or not, as we don't test initializing druntime before C main runs.
-Steve
Re: Can I create static c callable library?
On Thu, Sep 27, 2018 at 09:48:50PM +, Adam D. Ruppe via Digitalmars-d-learn wrote: > On Thursday, 27 September 2018 at 21:41:31 UTC, H. S. Teoh wrote: > > Though I'm not sure what will happen if your C program tries loading > > two or more D libraries that use this trick... is rt_init() > > idempotent? > > It just refcounts itself. Does that mean we could potentially make this "trick" the standard druntime initialization? Then we could make things work by default whether you compile a standalone executable or a shared library. Though I'm not sure what happens if multiple libraries each ship with their own copy of druntime... T -- Bomb technician: If I'm running, try to keep up.
Re: Can I create static c callable library?
On Thursday, 27 September 2018 at 21:41:31 UTC, H. S. Teoh wrote: Though I'm not sure what will happen if your C program tries loading two or more D libraries that use this trick... is rt_init() idempotent? It just refcounts itself.
Re: Can I create static c callable library?
On Thu, Sep 27, 2018 at 03:11:26PM -0600, Jonathan M Davis via
Digitalmars-d-learn wrote:
> On Thursday, September 27, 2018 6:16:13 AM MDT Atila Neves via Digitalmars-
> d-learn wrote:
[...]
> > Even easier, compile this C file and add the resulting object
> > file to your (now mostly) D static library:
> >
> > ---
> > extern int rt_init(void);
> > extern int rt_term(void);
> >
> > __attribute__((__constructor__)) void dinit(void) {
> > rt_init();
> > }
> > __attribute__((__destructor__)) void dterm(void) {
> > rt_term();
> > }
> > ---
> >
> > The C runtime will initialise the D runtime for you.
>
> That's a neat trick.
[...]
Indeed!
Though I'm not sure what will happen if your C program tries loading two
or more D libraries that use this trick... is rt_init() idempotent? If
not, it could lead to a fun mess on startup... :-D It also doesn't
address the very thorny issue of how to make multiple D libraries work
nicely with each other's copy of druntime, or how to make them share a
single druntime.
T
--
Без труда не выловишь и рыбку из пруда.
Re: Can I create static c callable library?
On Thursday, September 27, 2018 6:16:13 AM MDT Atila Neves via Digitalmars-
d-learn wrote:
> On Tuesday, 25 September 2018 at 14:13:50 UTC, Jacob Carlborg
>
> wrote:
> > On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis
> >
> > wrote:
> >> If you use -betterC, then it's trivial, because your D program
> >> is restricted to extern(C) functions and features which don't
> >> require druntime. It can also be done without -betterC (and
> >> thus with druntime), but it gets to be _way_ more of a pain,
> >> because it requires that you manually initialize druntime -
> >> either by forcing whatever is using your "C" library to call a
> >> specific function to initialize druntime before using any of
> >> its normal functions or by having every function in the
> >> library check whether druntime has been initialized yet and
> >> initialize it if it hasn't been before it does whatever it's
> >> supposed to do.
> >
> > Shouldn't it be possible to use a C initialization function,
> > i.e. pragma(crt_constructor) to initialize druntime? Then it
> > only needs to be initialized once and it's not required to
> > check if it's initialized all the time.
> >
> > --
> > /Jacob Carlborg
>
> Even easier, compile this C file and add the resulting object
> file to your (now mostly) D static library:
>
> ---
> extern int rt_init(void);
> extern int rt_term(void);
>
> __attribute__((__constructor__)) void dinit(void) {
> rt_init();
> }
> __attribute__((__destructor__)) void dterm(void) {
> rt_term();
> }
> ---
>
> The C runtime will initialise the D runtime for you.
That's a neat trick.
- Jonathan M Davis
Re: Can I create static c callable library?
On Tuesday, 25 September 2018 at 14:13:50 UTC, Jacob Carlborg
wrote:
On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis
wrote:
If you use -betterC, then it's trivial, because your D program
is restricted to extern(C) functions and features which don't
require druntime. It can also be done without -betterC (and
thus with druntime), but it gets to be _way_ more of a pain,
because it requires that you manually initialize druntime -
either by forcing whatever is using your "C" library to call a
specific function to initialize druntime before using any of
its normal functions or by having every function in the
library check whether druntime has been initialized yet and
initialize it if it hasn't been before it does whatever it's
supposed to do.
Shouldn't it be possible to use a C initialization function,
i.e. pragma(crt_constructor) to initialize druntime? Then it
only needs to be initialized once and it's not required to
check if it's initialized all the time.
--
/Jacob Carlborg
Even easier, compile this C file and add the resulting object
file to your (now mostly) D static library:
---
extern int rt_init(void);
extern int rt_term(void);
__attribute__((__constructor__)) void dinit(void) {
rt_init();
}
__attribute__((__destructor__)) void dterm(void) {
rt_term();
}
---
The C runtime will initialise the D runtime for you.
Re: Can I create static c callable library?
On Wednesday, 26 September 2018 at 09:54:22 UTC, John Burton wrote: Is there any documentation anywhere that deals with calling D from C? I could find plenty the other way round. I think I'll give up on the idea though, and rewrite the whole thing in D :) Rewriting it in D is a great idea ;) But for the record, much of what you've read about calling C from D applies the other way, too. You just need to write your D functions as extern(C), following the same approach to function signatures and types as you've read about, then declare the crossover functions and types in C. One gotcha to look out for is when you call a D function that allocates GC memory. In that case, you need to keep a reference to it alive on the D side. If it's only being allocated for use in C, you can call GC.addRoot [1] when you allocate the memory on the D side and GC.removeRoot [2] when you no longer need it. Also keep in mind that D variables thread-local, and if you need to access any of them in C from multiple threads they would better be declared as __gshared in D. [1] https://dlang.org/phobos/core_memory.html#.GC.addRoot [2] https://dlang.org/phobos/core_memory.html#.GC.removeRoot
Re: Can I create static c callable library?
On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis wrote: [...] Thanks everyone. Is there any documentation anywhere that deals with calling D from C? I could find plenty the other way round. I think I'll give up on the idea though, and rewrite the whole thing in D :)
Re: Can I create static c callable library?
On Tuesday, 25 September 2018 at 11:03:11 UTC, John Burton wrote: I need to write a library to statically link into a c program. Can I write this library in D? Will I be able to use proper D abilities like gc? Obviously the public interface will need to be basic c callable functions... I 'main' is a c program will this work? Yes, for example https://github.com/libmir/mir-optim It has *.cpp example.
Re: Can I create static c callable library?
On 9/25/18 10:13 AM, Jacob Carlborg wrote: On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis wrote: If you use -betterC, then it's trivial, because your D program is restricted to extern(C) functions and features which don't require druntime. It can also be done without -betterC (and thus with druntime), but it gets to be _way_ more of a pain, because it requires that you manually initialize druntime - either by forcing whatever is using your "C" library to call a specific function to initialize druntime before using any of its normal functions or by having every function in the library check whether druntime has been initialized yet and initialize it if it hasn't been before it does whatever it's supposed to do. Shouldn't it be possible to use a C initialization function, i.e. pragma(crt_constructor) to initialize druntime? Then it only needs to be initialized once and it's not required to check if it's initialized all the time. I don't know if that's the right call. pragma(crt_constructor) tasks run *before* C main. If you are initializing the runtime, it means you are running D static ctors. Since C initialization functions have no order to them, it's possible that some initialization functions in the D runtime are using uninitialized pieces of the C runtime. But of course, I'm not sure. I just wouldn't trust it if it were me. We don't test initializing the D runtime before C main is started (in which case, the C runtime is guaranteed to be set up). Does anyone know if the C runtime is set up before these functions are run? Is it guaranteed? -Steve
Re: Can I create static c callable library?
On Tuesday, 25 September 2018 at 12:05:21 UTC, Jonathan M Davis wrote: If you use -betterC, then it's trivial, because your D program is restricted to extern(C) functions and features which don't require druntime. It can also be done without -betterC (and thus with druntime), but it gets to be _way_ more of a pain, because it requires that you manually initialize druntime - either by forcing whatever is using your "C" library to call a specific function to initialize druntime before using any of its normal functions or by having every function in the library check whether druntime has been initialized yet and initialize it if it hasn't been before it does whatever it's supposed to do. Shouldn't it be possible to use a C initialization function, i.e. pragma(crt_constructor) to initialize druntime? Then it only needs to be initialized once and it's not required to check if it's initialized all the time. -- /Jacob Carlborg
Re: Can I create static c callable library?
On Tuesday, September 25, 2018 5:03:11 AM MDT John Burton via Digitalmars-d- learn wrote: > I need to write a library to statically link into a c program. > Can I write this library in D? > Will I be able to use proper D abilities like gc? Obviously the > public interface will need to be basic c callable functions... > > I 'main' is a c program will this work? If you use -betterC, then it's trivial, because your D program is restricted to extern(C) functions and features which don't require druntime. It can also be done without -betterC (and thus with druntime), but it gets to be _way_ more of a pain, because it requires that you manually initialize druntime - either by forcing whatever is using your "C" library to call a specific function to initialize druntime before using any of its normal functions or by having every function in the library check whether druntime has been initialized yet and initialize it if it hasn't been before it does whatever it's supposed to do. And of course, if you pass any GC-allocated memory out of the library, you have to worry about calling all of the appropriate GC functions so that it knows not to free it and knowing when to tell the GC that that memory can be freed. It's all very feasible and all very annoying. In general, it's far, far easier to write D programs that call into C code than to write C programs that call into D code. That's part of why some folks are so excited about -betterC. It makes it _way_ easier to write D libraries that can be called from C or C++ - though because you lose out on so many D features in the process (like the GC), whether it's even worth it is highly debatable. - Jonathan M Davis
Can I create static c callable library?
I need to write a library to statically link into a c program. Can I write this library in D? Will I be able to use proper D abilities like gc? Obviously the public interface will need to be basic c callable functions... I 'main' is a c program will this work?
