Segmentation fault on return from sub-routine

Given this functionCode:/* whichfltyp.c
* displays FileTp structure
* Bruce Irving 10/5/2020
*/

#include <stdio.h>
// #include <stdlib.h>
#include <string.h>
// #include <brlib.h>
#include "mysrch.h"

static struct FileTp
{ int ftn;
char ftd[10];
}/*;

static struct FileTp*/ fltyp[FTMAX+1] =
{ {0x0, "unknown"}, // 000 0
{0x1, "log"}, // 001 1
{0x2, "db"}, // 010 2
{0x4, "backup"}, // 100 4
{0x6, "dbbkp"}, // 110 6
{0xf, "all"} // 111 f
};

enum FTpSel { unknown, log = 1, db = 2, backup = 4, dbbkp = 6, all = 15 };

// displays description of ftp
char *whichfltyp( int ftp )
{ int i;
static char rt[10] ="";

if( ftp > FTMAX )
return NULL;
for( i = 0; i <= FTMAX; i++ )
if( fltyp[i].ftn == ftp )
break;
strcpy( rt, fltyp[i].ftd ); // to avoid accidental change to structure
return rt;
} // whichfltyp()and debuggingCode:bruce@pop-os:~/bin/src/mysrch$ gdb ./gnusrch
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Reading symbols from ./gnusrch...
(gdb) b fillpipe.c:89
Breakpoint 1 at 0x17c7: file fillpipe.c, line 89.
(gdb) r
Starting program: /home/bruce/bin/src/mysrch/gnusrch
[Detaching after vfork from child process 1307176]

Breakpoint 1, fillpipe () at fillpipe.c:89
warning: Source file is more recent than executable.
89 brtracef( "fillpipe %d: %3d: %s%s is %s\n",
(gdb) s
whichfltyp (ftp=21845) at whichfltyp.c:31
31 { int i;
(gdb) n
34 if( ftp > FTMAX )
(gdb) n
36 for( i = 0; i <= FTMAX; i++ )
(gdb) n
37 if( fltyp[i].ftn == ftp )
(gdb) n
36 for( i = 0; i <= FTMAX; i++ )
(gdb) n
37 if( fltyp[i].ftn == ftp )
(gdb) n
36 for( i = 0; i <= FTMAX; i++ )
(gdb) n
37 if( fltyp[i].ftn == ftp )
(gdb) p i
$1 = 2
(gdb) p ftp
$2 = 2
(gdb) n
38 break;
(gdb) n
39 strcpy( rt, fltyp[i].ftd ); // to avoid accidental change to structure
(gdb) p fltyp[i].ftd
$3 = "db\000\000\000\000\000\000\000"
(gdb) n
40 return rt;
(gdb) n
41 } // whichfltyp()
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
__strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:96
96 ../sysdeps/x86_64/multiarch/strlen-avx2.S: No such file or directory.
(gdb)Program received signal SIGSEGV, Segmentation fault.
__strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:96
96../sysdeps/x86_64/multiarch/strlen-avx2.S: No such file or directory.
I don't know why it would be calling strlen at this point.
I'm at a loss as to how to proceed. Any suggestions appreciated.
Bruce