Memory fault when attempting to run /dev/fd/1 as a script

[JohnoKing]

Reproducer with trace from ASan:

arch/linux.i386-64/bin/ksh /dev/fd/1
/home/johno/GitRepos/KornShell/ksh/src/lib/libast/cdt/dtstrhash.c:40:19: runtime error: unsigned integer overflow: 2166136238 * 16777619 cannot be represented in type 'unsigned int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/johno/GitRepos/KornShell/ksh/src/lib/libast/cdt/dtstrhash.c:40:19 
/home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/fcin.c:60:64: runtime error: applying non-zero offset 65536 to null pointer
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/fcin.c:60:64 
AddressSanitizer:DEADLYSIGNAL
=================================================================
==999828==ERROR: AddressSanitizer: SEGV on unknown address 0x000000010000 (pc 0x6476f8d73cdf bp 0x7ffc0c5c8750 sp 0x7ffc0c5c8660 T0)
==999828==The signal is caused by a WRITE memory access.
    #0 0x6476f8d73cdf in fcfopen /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/fcin.c:62:17
    #1 0x6476f8efb69d in sh_parse /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/parse.c:413:5
    #2 0x6476f8cb0851 in exfile /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/main.c:582:18
    #3 0x6476f8ca8ef3 in sh_main /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/main.c:348:2
    #4 0x6476f8ca3420 in main /home/johno/GitRepos/KornShell/ksh/src/cmd/ksh93/sh/pmain.c:41:2

This crash was first introduced in ksh93u- 2010-06-25 when the following line was added to sh_ioinit:

ksh/src/cmd/ksh93/sh/io.c

Line 473 in 9e2e6ca

sh_iostream(1);

I'm currently unsure why that sh_iostream call causes the buffer for fcin to become invalid.

[phidebian]

Posted #879 May be not ideal one, this one remove special case treatment of /dev/fd/... in the init() path based on the observation that the init() path don't do special case for /dev/stdout then I thougth /dev/fd/1 should go the same path as /dev/stdout.

If a real profond fix for the special case /dev/fd/1 is needed let me know

The fix do pass the tests on Ubuntu 24.04.2 LTS x86_64 and s390x