FreeCalypso > hg > freecalypso-tools
view target-utils/libprintf/README @ 965:2969032bdfac
fcup-smsend[mult]: fix buglet in K&R C NULL pointer passing
The only 100% safe way to pass a NULL pointer as a function argument
in K&R C is to cast 0 to a pointer type; failing to do so may cause
mysterious bugs (invalid stack frames or garbage in argument registers)
on 64-bit machines. This issue has already been fixed in most of
FC host tools, but I just found some missed spots: passing of NULL UDH
to PDU encoding functions in fcup-smsend[mult] in the case of single
(not concatenated) SMS.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Fri, 01 Sep 2023 07:33:51 +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).