Hi Renaud
I cannot presently step through the code on Windows to verify the cause of
the problem,
but looking at the code, I would _presume_ the reason is that symbol lookup is
cached on
Windows but not on Linux or OS X (at least by default).
Thus when we perform the second search for user_unif_rand, we find it in the
cache
rather than searching all the DLLs.
This happens because we did not specify a value for the PACKAGE parameter.
When we load a new DLL, the cache should probably be cleared or we
intelligently update it as necessary for the new DLLs on demand, i.e.
for a new search for a symbol we look in the new DLLs and then use the cache.
(This involves some book-keeping that could become convoluted.)
If we had specified a value for PACKAGE, e.g.
getNativeSymbolInfo("user_unif_rand", "rstream")
we would get the version in that package's DLL.
So this gives a workaround that you can use with just R code
findNativeSymbolInfo =
function(sym, dlls = rev(getLoadedDLLs())) {
for(d in dlls) {
z = getNativeSymbolInfo(sym, d)
if(!is.null(z))
return(z)
}
NULL
}
We'll think about whether to change the behaviour on Windows and how to do it
without affecting performance excessively.
Best,
D.
On 8/17/11 9:12 AM, Renaud Gaujoux wrote:
> Hi,
>
> When loading a package that provides the user-supplied RNG hook
> user_unif_rand, calling
> getNativeSymbolInfo("user_unif_rand") returns informations about the loaded
> symbol.
> I am using this to identify which package currently provides the RNG hook.
> The results are the same on windows and linux if only one library provides
> the hook.
>
> If one loads a second package that provides this hook, then on linux (Ubuntu
> 10.10), calling again
> getNativeSymbolInfo("user_unif_rand") returns the latest symbol information
> (which I presume is the correct result).
> On windows (XP and Vista) however the symbol information does not change
> (same pointer address) and the package data is
> NULL.
> See results for both systems below. I tested this with R 2.12.1, 2.13.0 and
> 2.13.1 on Windows.
>
> Is this a normal behaviour for dll loaded on Windows?
> Thank you.
>
> Renaud
>
>
> #####################
> # LINUX
> #####################
>> library(rlecuyer)
>> getNativeSymbolInfo("user_unif_rand")
> $name
> [1] "user_unif_rand"
>
> $address
> <pointer: 0x7ff55acffed0>
> attr(,"class")
> [1] "NativeSymbol"
>
> $package
> DLL name: rlecuyer
> Filename:
> /home/renaud/R/x86_64-pc-linux-gnu-library/2.12/rlecuyer/libs/rlecuyer.so
> Dynamic lookup: TRUE
>
> attr(,"class")
> [1] "NativeSymbolInfo"
>> library(rstream)
>> getNativeSymbolInfo("user_unif_rand")
> $name
> [1] "user_unif_rand"
>
> $address
> <pointer: 0x7ff55aaf58c0>
> attr(,"class")
> [1] "NativeSymbol"
>
> $package
> DLL name: rstream
> Filename:
> /home/renaud/R/x86_64-pc-linux-gnu-library/2.12/rstream/libs/rstream.so
> Dynamic lookup: TRUE
>
> attr(,"class")
> [1] "NativeSymbolInfo"
>
> #####################
> # WINDOWS
> #####################
>> library(rlecuyer)
>> getNativeSymbolInfo("user_unif_rand")
> $name
> [1] "user_unif_rand"
>
> $address
> <pointer: 0x6bb84fb8>
> attr(,"class")
> [1] "NativeSymbol"
>
> $package
> DLL name: rlecuyer
> Filename: C:/Program
> Files/R/R-2.13.1/library/rlecuyer/libs/i386/rlecuyer.dll
> Dynamic lookup: TRUE
>
> attr(,"class")
> [1] "NativeSymbolInfo"
>> library(rstream)
>> getNativeSymbolInfo("user_unif_rand")
> $name
> [1] "user_unif_rand"
>
> $address
> <pointer: 0x6bb84fb8>
> attr(,"class")
> [1] "NativeSymbol"
>
> $package
> NULL
>
> attr(,"class")
> [1] "NativeSymbolInfo"
>
>
>
>
>
>
>
>
> ###
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