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cgo: adjust return value location to account for stack copies.

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During a cgo call, the stack can be copied.  This copy invalidates
the pointer that cgo has into the return value area.  To fix this
problem, pass the address of the location containing the stack
top value (which is in the G struct).  For cgo functions which
return values, read the stktop before and after the cgo call to
compute the adjustment necessary to write the return value.

Fixes #8771

LGTM=iant, rsc
R=iant, rsc, khr
CC=golang-codereviews
https://golang.org/cl/144130043
This commit is contained in:
Keith Randall 2014-09-25 07:59:01 -07:00
parent dfaf1f71e6
commit 1b6807bb06
9 changed files with 161 additions and 50 deletions
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4
src/runtime/stack.c
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@ -827,7 +827,9 @@ runtime·shrinkstack(G *gp)
if(used >= oldsize / 4)
return; // still using at least 1/4 of the segment.
if(gp->syscallsp != 0) // TODO: can we handle this case?
// We can't copy the stack if we're in a syscall.
// The syscall might have pointers into the stack.
if(gp->syscallsp != 0)
return;
#ifdef GOOS_windows