Re: Memory Corruption Issue??
The fix turned out to be much simpler than what I had thought. https://github.com/D-Programming-Language/druntime/pull/1506
Re: Memory Corruption Issue??
Greetings I am using my D code as a dynamically loadable library that gets loaded at run time into C/C++ world. As discussed earlier on this thread, the GC does not mark TLS objects in this scenario and as a result the GC ends up collecting TLS objects even though these objects are still in use. More details of the issue can be found on the bug tracker https://issues.dlang.org/show_bug.cgi?id=15513 @Daniel provided two workarounds to this issue. One was to disable the GC altogether. I do not want to do that since my application generates too much data that necessitates regular sweeping. The other suggested workaround was to explicitly invoke GC.addRoot for all the TLS objects. This worked for me for some situations, but in other scenarios I am still facing crashes. I think these crashes may be resulting from the invisible TLS objects in phobos and druntime etc. I have confirmed that all these crashes subside if I disable GC altogether and also that the crashes do not happen if I make a D bases executable instead of DLL. I want to know if someone is working on this issue. If no one is, I am ready to spend time and get this behind me. Actually I have already worked on this bug and I think now I have a fair idea of what is happening. Is it the right forum to discuss my findings, or should I put my comments on bugzilla. I need some guidance in finding the right fix. Regards - Puneet
Re: Memory Corruption Issue??
Thanks Daniel I have added the testcase to a more obscure testcase that I had raised on Bugzilla earlier. https://issues.dlang.org/show_bug.cgi?id=15513 I want to request developers to show some love. Regards - Puneet
Memory Corruption Issue??
Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. The issue shows up only when I load a shared library created from D code from C and call some D functions from the C side. But since the program control is completely with the D code, and data structures in D get corrupted, I believe C has no role to play in the corruption. It is just that the memory layout of the executable, when the compiled D code is loaded from C, is helping in replicating the issue. I have spent almost a week in reducing this issue to less than 100 lines of code. Now I need the developers' love and help to get this issue fixed. There is some bleak chance that I am doing something wrong while loading the D library from C code. But otherwise it looks like a DMD memory corruption issue. Since two C, and one D files are involved in recreating the issue, I have put all the files on a github repository along with a makefile. I have been able to recreate the issue on two Ubuntu 14.04 64-bit machines. Generally the issue seems to be with static (thread local) variables that get allocated on heap. If I create many such variables, I get data corruption in some of these variables and sometimes I get segmentation fault. In this testcase that I have reduced, contents of a dynamic array are getting corrupted. Since all the data is being accessed from only one thread, there is no chance of a multicore race condition. To reproduce the issue, kindly clone my git repo (https://github.com/puneet/memerr.git). Change the path of the DMD installation (I have tested only with dmd-2.069.2) in the makefile and run make. $ git clone https://github.com/puneet/memerr.git # change DMD install path in memerr/makefile $ make I get an output like: $ make /home/puneet/local/dmd-2.069.2/linux/bin64/rdmd foo.d Start frop from D Successfully completed loop ./main Start frop from C 0 -> @�+ The last line is the content of an array which is actually filled with only dashes in the code. Kindly help. I want to make sure that I am not making a mistake before I file a bug on dlang bugzilla. Regards - Puneet
Re: Memory Corruption Issue??
Am Wed, 20 Jan 2016 09:12:57 + schrieb Bottled Gin: > Greetings > > I am struggling with strange memory corruption issues with > dmd-2.069.2 release. > Could be GC scanning issues. Can you try disabling the garbage collector and see if it still crashes?
Re: Memory Corruption Issue??
On Wednesday, 20 January 2016 at 09:12:57 UTC, Bottled Gin wrote: Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. [...] As a workaround you can mark Hash class as a shared final shared class Hash
Re: Memory Corruption Issue??
On Wednesday, 20 January 2016 at 11:49:29 UTC, Daniel Kozak wrote: On Wednesday, 20 January 2016 at 09:12:57 UTC, Bottled Gin wrote: Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. ... ./main Start frop from C 0 -> @�+ The last line is the content of an array which is actually filled with only dashes in the code. Kindly help. I want to make sure that I am not making a mistake before I file a bug on dlang bugzilla. Regards - Puneet Another workaround is to use GC.addRoot for dynamic allocated data in Dynamic.proc void proc () { import core.memory: GC; dash.length = 32; GC.addRoot(cast(void*)dash.ptr); dash[] = '-'; } And another one is hold pointer to data: class Dynamic { static char[] space; static char[] dash; char* dash_ptr; void rehash () { static Hash hash ; hash = new Hash; hash.clear(); } void proc () { import core.memory: GC; dash.length = 32; dash_ptr = dash.ptr; dash[] = '-'; } }
Re: Memory Corruption Issue??
On Wednesday, 20 January 2016 at 11:06:53 UTC, Daniel Kozak wrote: On Wednesday, 20 January 2016 at 09:12:57 UTC, Bottled Gin wrote: Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. [...] As a workaround you can mark Hash class as a shared final shared class Hash But this will change behavour because it will not be in TLS anymore
Re: Memory Corruption Issue??
On Wednesday, 20 January 2016 at 11:08:46 UTC, Daniel Kozak wrote: On Wednesday, 20 January 2016 at 11:06:53 UTC, Daniel Kozak wrote: On Wednesday, 20 January 2016 at 09:12:57 UTC, Bottled Gin wrote: Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. [...] As a workaround you can mark Hash class as a shared final shared class Hash But this will change behavour because it will not be in TLS anymore GC.disable seems help
Re: Memory Corruption Issue??
On Wednesday, 20 January 2016 at 09:12:57 UTC, Bottled Gin wrote: Greetings I am struggling with strange memory corruption issues with dmd-2.069.2 release. ... ./main Start frop from C 0 -> @�+ The last line is the content of an array which is actually filled with only dashes in the code. Kindly help. I want to make sure that I am not making a mistake before I file a bug on dlang bugzilla. Regards - Puneet Another workaround is to use GC.addRoot for dynamic allocated data in Dynamic.proc void proc () { import core.memory: GC; dash.length = 32; GC.addRoot(cast(void*)dash.ptr); dash[] = '-'; }
Re: Memory Corruption Issue??
Another workaround is to use GC.addRoot for dynamic allocated data in Dynamic.proc void proc () { import core.memory: GC; dash.length = 32; GC.addRoot(cast(void*)dash.ptr); dash[] = '-'; } And another one is hold pointer to data: class Dynamic { static char[] space; static char[] dash; char* dash_ptr; void rehash () { static Hash hash ; hash = new Hash; hash.clear(); } void proc () { import core.memory: GC; dash.length = 32; dash_ptr = dash.ptr; dash[] = '-'; } } Daniel, thanks for confirming the bug and for providing workaround. The second workaround (saving the pointer) will not work on my real project though. I have multiple threads and the TLS variable will have a different pointer on each thread. Also, can you please tell me how to addRoot an assoc array to GC. It seems there is no ptr property available for assoc arrays. Regards - Puneet
Re: Memory Corruption Issue??
V Wed, 20 Jan 2016 13:58:46 + Bottled Gin via Digitalmars-dnapsáno: > >> Another workaround is to use GC.addRoot for dynamic allocated > >> data in Dynamic.proc > >> > >> void proc () { > >> import core.memory: GC; > >> dash.length = 32; > >> GC.addRoot(cast(void*)dash.ptr); > >> dash[] = '-'; > >> } > > > > And another one is hold pointer to data: > > > > class Dynamic { > > static char[] space; > > static char[] dash; > > char* dash_ptr; > > void rehash () { > > static Hash hash ; > > hash = new Hash; > > hash.clear(); > > } > > void proc () { > > import core.memory: GC; > > dash.length = 32; > > dash_ptr = dash.ptr; > > dash[] = '-'; > > } > > } > > Daniel, thanks for confirming the bug and for providing > workaround. The second workaround (saving the pointer) will not > work on my real project though. I have multiple threads and the > TLS variable will have a different pointer on each thread. > > Also, can you please tell me how to addRoot an assoc array to GC. > It seems there is no ptr property available for assoc arrays. > > Regards > - Puneet > > > You can use cast(void *)aa; something like this: class Dynamic { static char[] space; static char[int] dash; void rehash () { static Hash hash ; hash = new Hash; hash.clear(); } void proc () { import core.memory: GC; //GC.addRoot(cast(void *)dash); // not here { dash[i] = '-'; } GC.addRoot(cast(void *)dash); // must be after allocation } } Be careful because you mast use addPtr after aa is initialized (you put something to it)