[Rd] Compiler warning: function returns address of local variable
radford at cs.toronto.edu
Mon Oct 7 13:06:28 CEST 2013
> > ..., my previous
> > dev-lang/R-2.10.1 ebuild package has been upgraded to R-3.0.1.
> > While compiling it, I have got the following compiler warning:
> > * QA Notice: Package triggers severe warnings which indicate that it
> > * may exhibit random runtime failures.
> > * main.c:1548:5: warning: function returns address of local variable
> > [enabled by default]
> > * Please do not file a Gentoo bug and instead report the above QA
> > * issues directly to the upstream developers of this software.
> > * Homepage: http://www.r-project.org/
> That is the whole point of that piece of C code, so please do report the
> Gentoo bug (their message is simply bogus) to them.
> And also read posting guide before posting: HTML mail is not allowed here.
> Brian D. Ripley, ripley at stats.ox.ac.uk
The message is certainly not "simply bogus". Returning the address of
a local variable is almost always a bug.
In this case, there is no real bug in R-3.0.1, since the result is
used for the low-level, system-dependent operation of determining the
direction of stack growth, but this is a very rare use. For the
compiler to issue such a warning is fully justified.
The warning could be avoided by using the approach taken in pqR, which
has the following routine in main.c:
/* Detemine whether the stack grows down (+1) or up (-1). Passed the
address of a local variable in the caller's stack frame.
This is put here, though called only from system.c, so that the compiler
will not be able to inline it. */
int R_stack_growth_direction (uintptr_t cvaraddr)
return (uintptr_t) &dummy < cvaraddr ? 1 : -1;
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