Re: sig2str and str2sig use in C++

[Daniel J Sebald]

On 06/04/2013 02:47 AM, Thien-Thi Nguyen wrote:
> () Paul Eggert<address@hidden>
> () Mon, 03 Jun 2013 15:28:24 -0700
>
>     extern char const allsigstr[];
>
>     This would consist of a concatenation of null-terminated strings,
>     one per name, terminated by an empty string.
>
>     [compile time wins]
>
> I seem to recall a paper several years back that argued against this
> approach based on ldso issues.  Drat, can't dredge the details...

I tried searching the Internet for such issues, but couldn't find any. 
What do you recall as being the loader problem?  The "extern" part?  Or 
use of a null string for termination?

I'm just thinking, Paul, if the null termination/index pointer idea were 
used throughout the string array, one could continue to use the

int sig2str (int, char *);

function in a backward compatible way.  (I had ruled that out with the 
run-time dynamic creation of such a thing, but with the indexing, there 
should be no re-entry problems.)  The fundamental string array would 
look like this, as an example:

{
"HUP",
"",
"INT",
"",
...
"STKFLT",
"",
"CHLD",
"CLD",
"",
"CONT",
"",
...
}

If the numname[] array then had a pointer to the first entry in the 
above string array it would produce the equivalent of the existing 
routine with the extension to continue reading null-terminated strings 
until the empty string.  However, this doesn't seem like an easy thing 
to sort through at compile-time unless the macro were written in such a 
way that it included duplicates.  For example (assuming there would 
never be more than two or three duplicates) the following illustrates 
conceptually (but perhaps syntactically it's dubious):

#define NUMNAME(name) { SIG##name, #name }
#define NUMNAME2(name1, name2) { ??? some kind of ##ifdef logic }
#define NUMNAME3(name1, name2, name3) { ??? some kind of ##ifdef logic }

/* Signal names and numbers.  Put the preferred name first.  */
static struct numname { int num; char const name[8]; } numname_table[] =
  {
    NUMNAME (HUP)
    NUMNAME (INT)
    NUMNAME (QUIT)
...
    NUMNAME2 (CHLD, CLD)
...
    { 0, "EXIT" }
  };

Dan