On Thu, 2019-01-03 at 11:23 +0000, Nicholas Wilson via Digitalmars-d-learn wrote: > On Thursday, 3 January 2019 at 08:35:17 UTC, Russel Winder wrote: > > Sorry about that, fairly obvious that the backtrace is needed > > in hindsight. :- ) > > > > #0 __GI___libc_free (mem=0xa) at malloc.c:3093 > > #1 0x000055555558f174 in dvb_file_free > > (dvb_file=0x5555555a1320) at dvb_file.d:282 > > #2 0x000055555558edcc in types.File_Ptr.~this() (this=...) at > > types.d:83 > > #3 0x0000555555574809 in > > channels.TransmitterData.__fieldDtor() (this=<error reading > > variable: Cannot access memory at address 0xa>) at > > channels.d:144 > > #4 0x000055555556aeda in channels.TransmitterData.__aggrDtor() > > (this=...) at channels.d:144 > > #5 0x000055555556ab53 in D main (args=...) at main.d:33 > > > > Which indicates that the destructor is being called before the > > instance has been constructed. Which is a real WTF. > > Not quite, this occurs as a TransmitterData object goes out of > scope at the end of main(stick a fflush'ed printf there to see):
I am not sure this analysis is correct. The code never reaches the end of main. > TransmitterData is a struct that has no destructor defined but > has a field of type File_Ptr that does. The compiler generates a > destructor, __aggrDtor, which calls the fields that have > destructors, __fieldDtor (e.g. the File_Ptr) which in turn calls > its destructor, File_Ptr.~this(). TransmitterData has a destructor defined but with no code in it. This used to work fine – but I cannot be certain which version of LDC that was. The problem does seem to be in the construction of the TransmitterData object because a destructor is being called on the File_Ptr field as part of the transmitterData constructor. > As you can see from the stack trace #3, the File_Ptr is null. The > solution to this is to either ensure it is initialised in the > constructor of TransmitterData, or account for it possibly being > null by defining a destructor for TransmitterData. For some reason it seems File_Ptr.~this() is being called before File_Ptr.this() in the TransmitterData.this(). This is totally weird. Having added some writeln statements: (gdb) bt #0 0x00005555555932e0 in dvb_file_free (dvb_file=0x0) at dvb_file.d:276 #1 0x0000555555592fbc in types.File_Ptr.~this() (this=...) at types.d:83 #2 0x000055555558cdf6 in _D3std6format__T14formattedWriteTSQBg5stdio4File17LockingTextWriterTaTS5types8File_PtrZQCtFKQChxAaQBcZk (w=..., fmt=..., _param_2=...) at /usr/lib/ldc/x86_64-linux-gnu/include/d/std/format.d:472 #3 0x000055555558c6a8 in _D3std5stdio4File__T5writeTAyaTS5types8File_PtrTaZQBeMFQBcQBbaZv (this=..., _param_0=..., _param_1=..., _param_2=10 '\n') at channels.d:1586 #4 0x00005555555749ce in _D3std5stdio__T7writelnTAyaTS5types8File_PtrZQBeFQzQxZv (_param_0=..., _param_1=...) at channels.d:3917 #5 0x000055555556af49 in _D8channels15TransmitterData6__ctorMFNcxAyaxkxE10libdvbv5_d8dvb_file16dvb_file_formatsZSQDiQDc (this=..., path=..., delsys=0, format=libdvbv5_d.dvb_file.dvb_file_formats.FILE_DVBV5) at channels.d:143 #6 0x000055555556aa9c in D main (args=...) at main.d:34 -- Russel. =========================================== Dr Russel Winder t: +44 20 7585 2200 41 Buckmaster Road m: +44 7770 465 077 London SW11 1EN, UK w: www.russel.org.uk
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