R devel - Nov 1999 - R_OpenSiteFile: Do not use a null ptr as filename in fopen (PR#312)

I get crashes when I call R without any arguments and having no
environment variables R_PROFILE and RPROFILE.

The reason is, that in unix/sys-common.c in R_OpenSiteFile() fopen 
is called with a null ptr as filename (because this is the outcome 
of getenv()).

Although most compilers seem to interpret this as "file not found",
this is an undefined behavior concerning to all C standards I could get
hold of.

A request in comp.lang.c gave the following response:
...
Your program should crash. If you might get a NULL pointer as
a filename, you should have a conditional statement to handle
that case.
...

So I would suggest to test for the return value of getenv, before 
using it as filename in fopen.

--please do not edit the information below--

Version:
 platform = hppa1.1-hp-hpux10.20
 arch = hppa1.1
 os = hpux10.20
 system = hppa1.1, hpux10.20
 status = 
 status.rev = 0
 major = 0
 minor = 65.0
 year = 1999
 month = August
 day = 27
 language = R

Search Path:
 .GlobalEnv, Autoloads, package:base

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On Thu, Nov 04, 1999 at 10:09:05AM +0100, hoffmann@ehmgs2.et.tu-dresden.de
wrote:
> 
> The reason is, that in unix/sys-common.c in R_OpenSiteFile() fopen 
> is called with a null ptr as filename (because this is the outcome 
> of getenv()).
> 
> Although most compilers seem to interpret this as "file not
found",
> this is an undefined behavior concerning to all C standards I could get
> hold of.
> 
> A request in comp.lang.c gave the following response:
> ...
> Your program should crash. If you might get a NULL pointer as
> a filename, you should have a conditional statement to handle
> that case.
> ...
>
The same happens also under Windows where, for this reason, 
'R_fopen' is defined as
 
FILE *R_fopen(const char *filename, const char *mode)
{
    if (!filename)
	return NULL;
    return (fopen(filename, mode));
}

g.

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