Description of problem:

regcomp() should correctly find the occurences of '{ ' in a string, since it is said: (man 7 regex) 
A  '{'  followed by a character other than a digit is an ordinary character, not the beginning of a bound(!).

Version-Release number of selected component (if applicable):


How reproducible:
Always.

Steps to Reproduce:
1. compile and run this small C code below (slightly edited copy of the man example). 
2. the result is OK on, e.g., OSX. Not on Mageia 8 (glibc 2.32-30) and not on Mageia Cauldron (glibc 2.36-30 at the time of writing) where an error is issued. 

Instead, the program using regcomp(), should find the positions of '{ ' in the string "1234 G!t!rk{ ss { zz...\n" 

Please notet hat the problem exists also with '{' and not '{ ' as I demonstrate in the below program. I believe the sentence " '{' followed by a character..." holds even if there is no character at all (and indeed the OSX version behaves the same with '{'), so the exact extent of this glibc bug is to be determined.

3. the code:
      #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <regex.h>

       #define ARRAY_SIZE(arr) (sizeof((arr)) / sizeof((arr)[0]))

       static const char *const str =  "1234 G!t!rk{ ss { zz...\n";
       static const char *const re = "{ ";

       int main(void)
       {
           static const char *s = str;
           regex_t     regex;
           regmatch_t  pmatch[1];
           regoff_t    off, len;
int cflags = REG_EXTENDED;
 int res=regcomp(&regex, re, cflags);
 if (res) {
   printf("regcomp error:");
   if (res == REG_BADBR   ) printf(" REG_BADBR   ");
   if (res == REG_BADPAT  ) printf(" REG_BADPAT  ");
   if (res == REG_BADRPT  ) printf(" REG_BADRPT  ");
   if (res == REG_EBRACE  ) printf(" REG_EBRACE  ");
   if (res == REG_EBRACK  ) printf(" REG_EBRACK  ");
   if (res == REG_ECOLLATE) printf(" REG_ECOLLATE");
   if (res == REG_ECTYPE  ) printf(" REG_ECTYPE  ");
   /* if (res == REG_EEND    ) printf(" REG_EEND    "); */
   if (res == REG_EESCAPE  ) printf(" REG_EESCAPE  ");
   if (res == REG_EPAREN  ) printf(" REG_EPAREN  ");
   if (res == REG_ERANGE  ) printf(" REG_ERANGE  ");
   /* if (res == REG_ESIZE   ) printf(" REG_ESIZE   ");  */
   if (res == REG_ESPACE  ) printf(" REG_ESPACE  ");
   if (res == REG_ESUBREG ) printf(" REG_ESUBREG ");
   printf("\n");
  exit(EXIT_FAILURE);
 }

           printf("String = \"%s\"\n", str);
           printf("Matches:\n");

           for (int i = 0; ; i++) {
               if (regexec(&regex, s, ARRAY_SIZE(pmatch), pmatch, 0))
                   break;

               off = pmatch[0].rm_so + (s - str);
               len = pmatch[0].rm_eo - pmatch[0].rm_so;
               printf("#%d:\n", i);
               printf("offset = %jd; length = %jd\n", (intmax_t) off,
                       (intmax_t) len);
               printf("substring = \"%.*s\"\n", len, s + pmatch[0].rm_so);

               s += pmatch[0].rm_eo;
           }

           exit(EXIT_SUCCESS);
       }