[Rd] xrealloc namespace conflict

[Patrick Perry]

I've done a bit more investigation into this issue. Here is my current 
understanding of the situation:

1. I have a package on CRAN (corpus-0.3.1) that passes tests on all 
platforms except for Linux.
2. My package defines a C function, "xrealloc", for internal use.
3. The libreadline library that R links to defines a different version 
of "xrealloc".
4. On Linux, when I load my package, references to "xrealloc" get linked 
to the libreadline version of that function.
5. This causes one of my tests to fail, calling exit(2), because the 
libreadline version of xrealloc does not allow calls of the form 
"xrealloc(ptr, 0)".

I can work around this issue pretty easily, by either renaming my 
version of xrealloc to something else, or by avoiding calls of the form 
"xrealloc(ptr, 0)". So, this is not a major issue, but it's a little 
unsettling to see this behavior when my package does not explicitly link 
to or use anything from libreadline.

Is there a reason this behavior is only manifesting on Linux? Is there 
something wrong with the way I'm compiling my package on that platform? 
Is this just some quirk about the way R is loading dynamic libraries on 
Linux? I'd appreciate any insight into the issue.


Patrick

p.s. Here are some references:

My package Makevars are at 
https://github.com/patperry/r-corpus/blob/master/src/Makevars ; my 
version of "xrealloc" is in corpus/src/xalloc.c

You can see the source for the libreadline xrealloc at 
https://github.com/JuliaLang/readline/blob/master/xmalloc.c#L67


Patrick Perry wrote:
>
> I have a package on CRAN now (corpus-0.3.1) that is currently failing
> tests on Linux, but passing on all other architectures:
>
> https://cran.r-project.org/web/checks/check_results_corpus.html
>
> I believe that the issue arrises from a namespace class between
> "xrealloc", which my package provides for internal use, but which R
> also seems to provide (possibly as part of TRE in
> src/extra/tre/xmalloc.c). It looks like my package is not picking up
> my custom xrealloc, but using an xrealloc provided by R.
>
> Besides the fact that I am linking to the wrong xrealloc, I think my
> tests are failing for the same reason that the following code
> segfaults on Linux (Debian, with R 3.4.0):
>
> test <- inline::cfunction(language='C',
>     otherdefs='void *xmalloc(size_t); void *xrealloc(void *, size_t);',
>     body = 'void *ptr = xmalloc(256); xrealloc(ptr, 0); return
> R_NilValue;')
> test()
> ## xrealloc: out of virtual memory
>
> It seems that the R xrealloc doesn't like being given a size of 0,
> even though this behavior is well-defined for realloc (it should free
> the memory). Based on my failing CRAN tests, it looks like this is a
> Linux-specific issue.
>
> Is there a way to modify my Makevars to force the linker to choose my
> version of xrealloc for my package-specific code? My current Makevars
> are at https://github.com/patperry/r-corpus/blob/master/src/Makevars
>
> Thanks in advance for any help.
>
>
> Patrick


> Patrick Perry <mailto:pperry at stern.nyu.edu>
> May 6, 2017 at 5:36 PM
> I have a package on CRAN now (corpus-0.3.1) that is currently failing 
> tests on Linux, but passing on all other architectures:
>
> https://cran.r-project.org/web/checks/check_results_corpus.html
>
> I believe that the issue arrises from a namespace class between 
> "xrealloc", which my package provides for internal use, but which R 
> also seems to provide (possibly as part of TRE in 
> src/extra/tre/xmalloc.c). It looks like my package is not picking up 
> my custom xrealloc, but using an xrealloc provided by R.
>
> Besides the fact that I am linking to the wrong xrealloc, I think my 
> tests are failing for the same reason that the following code 
> segfaults on Linux (Debian, with R 3.4.0):
>
> test <- inline::cfunction(language='C',
>     otherdefs='void *xmalloc(size_t); void *xrealloc(void *, size_t);',
>     body = 'void *ptr = xmalloc(256); xrealloc(ptr, 0); return 
> R_NilValue;')
> test()
> ## xrealloc: out of virtual memory
>
> It seems that the R xrealloc doesn't like being given a size of 0, 
> even though this behavior is well-defined for realloc (it should free 
> the memory). Based on my failing CRAN tests, it looks like this is a 
> Linux-specific issue.
>
> Is there a way to modify my Makevars to force the linker to choose my 
> version of xrealloc for my package-specific code? My current Makevars 
> are at https://github.com/patperry/r-corpus/blob/master/src/Makevars
>
> Thanks in advance for any help.
>
>
> Patrick
>


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