FreeCalypso > hg > freecalypso-tools
view target-utils/libprintf/README @ 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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The present libprintf is a very light printf implementation that is well-suited for simple bare-metal programs like loadagent; in the present case it overrides the much heavier printf implementation in newlib. Programs like the present loadagent only need printf in order to scribble on the serial console port, and the most sensible implementation is to have the "character output" function from the guts of printf point directly to the physical UART output routine, or a trivial wrapper that turns \n into \r\n. In contrast, newlib's version would pull in the complete FILE table infrastructure and malloc etc - maybe OK for more complex embedded programs that use those facilities for other things under a bona fide RTOS, but it would be disgusting to pull that stuff in for a minimal program like ours. The present printf implementation has been used earlier by the same author (Michael Spacefalcon) in the StarMON family of PowerPC bootloaders, and in my MC68x302-based SDSL CPE devices (Hack-o-Rocket and OSDCU).