code review 88550043: liblink: add leaf bit to object file format

liblink: add leaf bit to object file format

Without the leaf bit, the linker cannot record
the correct frame size in the symbol table, and
then stack traces get mangled. (Only for ARM.)

Fixes issue 7338.
Fixes issue 7347.

[rsc, 2014-04-16 17:40:36]

Hello iant (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[iant, 2014-04-16 20:04:28]

LGTM

https://codereview.appspot.com/88550043/diff/40001/src/cmd/ld/pcln.c
File src/cmd/ld/pcln.c (right):

https://codereview.appspot.com/88550043/diff/40001/src/cmd/ld/pcln.c#newcode176
src/cmd/ld/pcln.c:176: off = setuint32(ctxt, ftab, off, ctxt->cursym->locals +
PtrSize*!ctxt->cursym->leaf);
That is sort of elegant, I guess, but can we just write
    frameptrsize = PtrSize;
    if (ctxt->cursym->leaf)
        frameptrsize = 0;

[rsc, 2014-04-16 21:11:48]

*** Submitted as https://code.google.com/p/go/source/detail?r=993231085fbf ***

liblink: add leaf bit to object file format

Without the leaf bit, the linker cannot record
the correct frame size in the symbol table, and
then stack traces get mangled. (Only for ARM.)

Fixes issue 7338.
Fixes issue 7347.

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/88550043

[gobot, 2014-04-16 21:37:13]

This CL appears to have broken the windows-amd64 builder.
See http://build.golang.org/log/386a00b3ac3147a7f33d114bc3af3d494b87a649