Varargs in jansson using json_vpack_ex

[Martin Assarsson]

Hi!

I'm using jansson in a multithreaded program on an embedded arm-system.

This system is build with "buildroot" using bussybox and uclibc.

When using the construction below I get heap corruption and use a different aproach at the moment.

Is there anybody else experiencing this problem?

Any solution?

I would like to reinstate the varargs approach.

va_list ap;

va_start(ap, fmt);

obj = json_vpack_ex(NULL, 0, fmt, ap);

va_end(ap);

  // Martin

[Petri Lehtinen]

json_vpack_ex() uses va_copy() to make it possible to pass ap to
another function as an argument. If va_copy() is not available as a
macro, Jansson uses either __va_copy or simple memcpy() as a fallback.

Do you happen to know whether uclibc supports va_copy() on your
platform?

Petri

[Martin Assarsson]

Thanks for quick response!

Afaik this depends on compiler compliance with C99. My compiler has this version

arm-unknown-linux-uclibcgnueabi-gcc (Buildroot 2012.05) 4.5.3

Correct me if I'm wrong, but it should mean that it has a va_copy.

  // Martin

[Petri Lehtinen]

Yeah, va_copy() should be ok in this case. I can't think of any other
(Jansson related) causes for your problem. Let us know if you find out
how to make it work.

Petri

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[Martin Assarsson]

Thanks for your time, I will dig in to it later.

  // Martin