Re: [I::C] Why does it segfault?

When loading the respective core file into gdb, it indicated that the segfault had occurred when calling SvLEN_set():

$ gdb /usr/local/bin/perl  core
...
Core was generated by `/usr/local/bin/perl -lw ./959669.pl 128'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007f8382eb85c5 in new (classname=0x11b1170 "fred", bits=<optim
+ized out>) at test.xs:23
23        SvLEN_set( obj, bytes );
(gdb) q
[download]

My guess would be this is because the SV created with nevSV(0) doesn't yet have a LEN field. Using newSV_type(SVt_PV) instead fixed the issue (AFAICT), i.e.

...
    obj = newSV_type(SVt_PV);
    SvPOK_only( obj );
    SvPV_set( obj, vector );
    SvLEN_set( obj, bytes );
    SvCUR_set( obj, bytes );
...

__END__
$ ./959669.pl 128
...
SV = PVMG(0x1068f90) at 0xfb8d80
  REFCNT = 1
  FLAGS = (OBJECT,POK,pPOK)
  IV = 0
  NV = 0
  PV = 0x149cfa0 "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
  CUR = 16
  LEN = 16
  STASH = 0xfd4f08    "fred"
[download]

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Re^2: [I::C] Why does it segfault? by BrowserUk (Patriarch) on Mar 15, 2012 at 06:08 UTC
Thanks Eliya. Makes sense... Now :) With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. The start of some sanity?	[reply]
Re^2: [I::C] Why does it segfault? by ikegami (Patriarch) on Mar 16, 2012 at 21:25 UTC
My guess would be this is because the SV created with nevSV(0) doesn't yet have a LEN field. It doesn't have a body at all. Using newSV_type(SVt_PV) instead fixed the issue (AFAICT), i.e. Shorter: [ nevermind, that'll copy the vector instead of uisng it. ] `newSVpvn(vector, bytes)` [download]	[reply] [d/l]