betterC on Win32: execute shared static ctors+dtors by WalterBright · Pull Request #6956 · dlang/dmd

WalterBright · 2017-07-01T06:24:58Z

This uses the mechanism Digital Mars C++ uses to call C++ static constructors and destructors to call D shared static constructors and destructors in -betterC mode.

Each C compiler does it differently, so some research is necessary to figure it out for other platforms.

dlang-bot · 2017-07-01T06:24:58Z

Thanks for your pull request, @WalterBright!

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If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

CyberShadow · 2017-07-01T08:25:05Z

test/runnable/betterCsharedctor.d

@@ -0,0 +1,21 @@
+/* REQUIRED_ARGS: -betterC
+ * PERMUTE_ARGS:
+ */


Can TEST_OUTPUT be used here? Currently nothing tests that the ctors/dtors are actually executed.

Testing the output will come when the other platforms are supported.

oops

jpf91 · 2017-07-01T09:11:30Z

For linux it's usually just placing a function pointer into a specific section.

👍 to the idea and more betterC work. One thing I was wondering though is that the betterC constructors then have slightly different runtime semantics (construction order is not guaranteed and cyclic module contructor dependencies therefore will be supported in betterC mode). I'm not sure if it is a good idea to change semantics with a compiler switch.

An alternative is to use an @CContructor UDA and normal module level functions, I think LDC already does that. Another benefit of the UDA approach is that you now can easily implement multiple named betterC constructors per module.

Ping @andralex as this is some kind of language change / discussion.

WalterBright · 2017-07-01T10:43:07Z

Don't pull this yet, I have a better idea.

WalterBright · 2017-07-01T20:23:31Z

Ok, better idea done.

andralex

Cool beans. This should come with a changelog entry and documentation. Please fix the bug and perhaps add more test (only ctor/dtor).

andralex · 2017-07-01T21:05:13Z

src/ddmd/glue.d

+        {
+            if (m.ssharedctor)
+                objmod.setModuleCtorDtor(m.ssharedctor, true);
+            if (m.ssharedctor)


BUG should be if (m.sshareddtor)

danged copy/pasta errors!

WalterBright · 2017-07-01T21:26:01Z

@andralex done

WalterBright · 2017-07-02T04:52:05Z

While this is waiting, there's #6957 for the non-controversial bits.

ibuclaw · 2017-07-27T18:11:27Z

Perhaps -betterC should become a meta-flag for other features. Same as what is done for -release.

jacob-carlborg · 2017-08-13T12:51:59Z

Is this the same as __attribute__((constructor)) on GCC/Clang? In that case I agree with @jpf91 that it should be a separate functionality, like a UDA or pragma on a regular function. This is a useful feature to have even when betterC is not used.

We also already have this for ELF targets (Linux and FreeBSD). It was added for the implementation of dynamic libraries.

schveiguy

I'm against such a change, since D users expect to have proper ordering of D static ctor/dtors regardless of link order. I would recommend instead to simply use the C compiler's feature with that compiler. I can't imagine chasing a bug due to linker order is going to be fun when you switch to -betterC mode.

Just giving my opinion for what it's worth, not expecting a response or acceptance.

schveiguy · 2017-10-03T23:50:21Z

changelog/betterC-STI-STD.dd

+
+Although D guarantees that static construction for imports occurs first,
+no such ordering guarantee is available with -betterC. Typically, however, the order
+matches the order in which object files are presente to the linker.


CyberShadow · 2017-10-04T00:05:34Z

I'm against such a change, since D users expect to have proper ordering of D static ctor/dtors regardless of link order.

Not having switches that subtly change language semantics is probably a good idea.

How about allowing the use of this feature through extern(C) static this() { ... } regardless of -betterC?

schveiguy · 2017-10-04T00:12:32Z

How about allowing the use of this feature through extern(C) static this() { ... } regardless of -betterC?

I don't like that either, because I guarantee there is some poor soul who put extern(C): at the top of their module, without putting extern(D) in front of their static ctor/dtor, and now you will drastically change the behavior.

FYI: there is a discussion about this very thing here: https://issues.dlang.org/show_bug.cgi?id=17747

jacob-carlborg · 2017-10-04T09:05:30Z

It can be implemented using a UDA or pragma, like for GDC and LDC.

MartinNowak · 2017-10-06T01:00:49Z

Each C compiler does it differently, so some research is necessary to figure it out for other platforms.

See #7182

MartinNowak · 2017-10-06T10:49:29Z

We might close this in favor of #7182

For the unlikely need of a codebase to support both, D and D -betterC, version (D_betterC) could be used to switch between shared static this() and pragma(crt_constructor).

andralex · 2017-12-12T20:07:15Z

Let's go with #7182. Further improvements will come on top of it.

bitraft · 2017-12-20T04:28:32Z

Hi, @andralex @WalterBright

please check on https://issues.dlang.org/show_bug.cgi?id=18100

crt_constructor need to allow set immutable(which mean it only should be call once, and can not been call from main function). If we simple use extern(C) shared static this will fix all problem.

WalterBright force-pushed the betterC-STI-STD branch from fbd7c4d to 2b0fc7c Compare July 1, 2017 06:27

CyberShadow previously approved these changes Jul 1, 2017

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WalterBright force-pushed the betterC-STI-STD branch from 2b0fc7c to 536328b Compare July 1, 2017 20:22

andralex requested changes Jul 1, 2017

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WalterBright force-pushed the betterC-STI-STD branch 2 times, most recently from d8de3b7 to 78cbde8 Compare July 1, 2017 21:24

WalterBright force-pushed the betterC-STI-STD branch from 78cbde8 to 7329086 Compare July 1, 2017 21:39

WalterBright mentioned this pull request Jul 2, 2017

refactor: convert Obj.funcptr() to Obj.setModuleCtorDtor() #6957

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betterC on Win32: execute shared static ctors+dtors

d3271c0

WalterBright force-pushed the betterC-STI-STD branch from 7329086 to d3271c0 Compare July 4, 2017 00:46

jpf91 mentioned this pull request Jul 27, 2017

Add @attribute cctor/cdtor for C runtime constructors / destructors D-Programming-GDC/gdc#183

Closed

MartinNowak mentioned this pull request Sep 30, 2017

implement open GC registry dlang/druntime#1924

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schveiguy reviewed Oct 3, 2017

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MartinNowak mentioned this pull request Oct 6, 2017

fix 17868 - add pragma(crt_con-/destructor) #7182

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andralex closed this Dec 12, 2017

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