R help - Mar 1999 - .C and character

Hi,

I had a problem passing characters from R into c-code by dyn.load() and .C().

test.c:
	void R2Cdouble(double *db)
	{
		printf("\n my double: %f \n", db[0]);
	}

test.R:
	dyn.load("mylib.so");
	.C("R2Cdouble", as.double(0.5));

worked fine, but

test1.c:
	void R2Cstr(char *str)
	{
		printf("\n my char: %s \n", str[0]);
	}

test1.R:
	dyn.load("mylib.so");
	.C("R2Cdouble", as.character("test"));

caused a segmentation fault (Linux 2.0.36, R-0.62.4).

Is there a mechanism to do that?


Torsten  

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>>>>> "Torsten" == Torsten Hothorn <hothorn at
amadeus.statistik.uni-dortmund.de> writes:
  Torsten> Hi, I had a problem passing characters from R into c-code
  Torsten> by dyn.load() and .C().

  Torsten> test1.c: void R2Cstr(char *str) { printf("\n my char: %s
  Torsten> \n", str[0]); }

You must declare str as char **str.  The basic character vector in R
is a vector of strings, not a vector of characters.  Notice that the
way you are printing it assumes that str[0] is char *, not char.
If you change your example to

test1.c:
	void R2Cstr(char **str)
	{
		printf("\n my char: %s \n", str[0]);
	}

test1.R:
	dyn.load("mylib.so");
	.C("R2Cdouble", as.character("test"));

it should work.
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