FreeCalypso > hg > freecalypso-tools
view rvinterf/libg23/fmtdispatch.c @ 465:003e48f8ebe1
rvinterf/etmsync/fsnew.c: cast 0 to (char *) for execl sentinel
I generally don't use NULL and use plain 0 instead, based on a "NULL
considered harmful" discussion on the classiccmp mailing list many aeons
ago (I couldn't find it, and I reason that it must have been 2005 or
earlier), but a recent complaint by a packager sent me searching, and I
found this:
https://ewontfix.com/11/
While I don't give a @#$% about "modern" systems and code-nazi tools,
I realized that passing a plain 0 as a pointer sentinel in execl is wrong
because it will break on systems where pointers are longer than the plain
int type. Again, I don't give a @#$% about the abomination of x86_64 and
the like, but if anyone ever manages to port my code to something like a
PDP-11 (16-bit int, 32-bit long and pointers), then passing a plain 0
as a function argument where a pointer is expected most definitely won't
work: if the most natural stack slot and SP alignment unit is 16 bits,
fitting an int, with longs and pointers taking up two such slots, then
the call stack will be totally wrong with a plain 0 passed for a pointer.
Casting the 0 to (char *) ought to be the most kosher solution for the
most retro systems possible.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Mon, 11 Feb 2019 00:00:19 +0000 |
parents | e7502631a0f9 |
children |
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/* * This libg23 module exports the format_g23_packet() function, which * validates the packet, then dispatches it to format_g23_trace(), * format_g23_sysprim() or format_g23_psprim() as appropriate, or * prints it in raw hex if malformed. */ #include <sys/types.h> #include <stdio.h> #include <string.h> #include <strings.h> static int basic_checks(rxpkt, rxpkt_len) u_char *rxpkt; { int i, c; if (rxpkt_len < 17) return(0); /* check version bits in the header byte */ if ((rxpkt[1] & 0xC0) != 0x80) return(0); /* check the length */ c = rxpkt[2] | rxpkt[3] << 8; if (c + 4 != rxpkt_len) return(0); /* ensure that the "from" and "to" are printable ASCII */ for (i = 8; i < 16; i++) { c = rxpkt[i]; if (c < ' ' || c > '~') return(0); } /* basic checks pass */ return(1); } static int psprim_extra_checks(rxpkt, rxpkt_len) u_char *rxpkt; { int i, c; if (rxpkt_len < 24) return(0); /* "original rcvr" field needs to be printable ASCII */ for (i = 16; i < 20; i++) { c = rxpkt[i]; if (c < ' ' || c > '~') return(0); } /* checks pass */ return(1); } static void print_unknown_bin(rxpkt, rxpkt_len, outbuf) u_char *rxpkt; char *outbuf; { int i; char *dp; dp = outbuf; strcpy(dp, "GPF UNK:"); dp += 8; for (i = 1; i < rxpkt_len; i++) { sprintf(dp, " %02X", rxpkt[i]); dp += 3; } *dp = '\0'; } static void print_old_ascii(rxpkt, rxpkt_len, outbuf) u_char *rxpkt; char *outbuf; { char *dp; int txtlen = rxpkt_len - 1; dp = outbuf; strcpy(dp, "GPF ASC: "); dp += 9; bcopy(rxpkt + 1, dp, txtlen); dp += txtlen; *dp = '\0'; } static int is_old_ascii(rxpkt, rxpkt_len) u_char *rxpkt; { int i, c; for (i = 1; i < rxpkt_len; i++) { c = rxpkt[i]; if (c < ' ' || c > '~') return(0); } return(1); } static void print_malformed(rxpkt, rxpkt_len, outbuf) u_char *rxpkt; char *outbuf; { if (is_old_ascii(rxpkt, rxpkt_len)) print_old_ascii(rxpkt, rxpkt_len, outbuf); else print_unknown_bin(rxpkt, rxpkt_len, outbuf); } void format_g23_packet(rxpkt, rxpkt_len, outbuf) u_char *rxpkt; char *outbuf; { if (!basic_checks(rxpkt, rxpkt_len)) { print_malformed(rxpkt, rxpkt_len, outbuf); return; } /* dispatch by type */ switch (rxpkt[1] & 0x30) { case 0x10: /* PS primitive */ if (psprim_extra_checks(rxpkt, rxpkt_len)) format_g23_psprim(rxpkt, rxpkt_len, outbuf); else print_malformed(rxpkt, rxpkt_len, outbuf); return; case 0x20: /* trace */ format_g23_trace(rxpkt, rxpkt_len, outbuf); return; case 0x30: /* system primitive */ format_g23_sysprim(rxpkt, rxpkt_len, outbuf); return; default: print_malformed(rxpkt, rxpkt_len, outbuf); } }