static symbols too?

June 5, 2010

(This article was first published on BioStatMatt, and kindly contributed to R-bloggers)

Continuing in the context of this previous post

1. Select a static symbol from the R sources, like Connections

$ grep "static Rconnection Connections" src/main/connections.c
static Rconnection Connections[NCONNECTIONS];

2. Get its address

$ objdump -t `R RHOME`/bin/exec/R | awk '/ Connections/ {print $1}'

3. Use the symbol

> library(inline)
> code <- "
+     typedef struct { char *class, *description; } *Rconnection;
+     Rconnection *Connections = (Rconnection*)0x000000000093b700;
+     return mkString(Connections[0]->description);
+ "
> ConZeroDesc <- cfunction(signature(), code, language="C")
> ConZeroDesc()
[1] "stdin"

This effect could probably be prevented by selecting additional compiler and/or and linker options.

P.S. Nice job Oleg Sklyar, Duncan Murdoch, Mike Smith, Dirk Eddelbuettel, Romain Francois with inline-0.3.5

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