Since gccgo can trace back through C code as easily as Go code, we
should print C functions in the traceback.
This worked before https://golang.org/cl/31230 for a dumb reason. The
default value for runtime.traceback_cache was, and is, 2 << 2, meaning
to print all functions. The old C code for runtime_parsedebugvars
would return immediately and do nothing if the environment variable
GODEBUG was not set (if GODEBUG was set it would later call
setTraceback. The new Go code for runtime.parsedebugvars does not
return immediately if GODEBUG is not set, and always calls
setTraceback. Either way, if GOTRACEBACK is not set, setTraceback
would set traceback_cache to 1 << 2, meaning to only print non-runtime
functions and having the effect of not printing plain C functions.
Keep the current handling of GODEBUG/GOTRACEBACK, which matches the gc
library, but add an extra check to print C functions by default.
Reviewed-on: https://go-review.googlesource.com/33717
From-SVN: r243083
While we're at it, update the runtime/debug package, and start running
its testsuite by default. I'm not sure why runtime/debug was not
previously updated to 1.7. Doing that led me to fix some minor aspects
of runtime.Stack and the C function runtime/debug.readGCStats.
Reviewed-on: https://go-review.googlesource.com/31251
From-SVN: r241261
Also create a gccgo version of some of the traceback code in
traceback_gccgo.go, replacing some code currently in C.
This required modifying the compiler so that when compiling the runtime
package a slice expression does not cause a local array variable to
escape to the heap.
Reviewed-on: https://go-review.googlesource.com/31230
From-SVN: r241189
Ian Lance Taylor