Re: disable -Warray-bounds in libgo (PR 101374)

[Ian Lance Taylor via Gcc-patches]

On Thu, Jul 8, 2021 at 11:16 PM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Thu, Jul 8, 2021 at 8:02 PM Martin Sebor via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Hi Ian,
> >
> > Yesterday's enhancement to -Warray-bounds has exposed a couple of
> > issues in libgo where the code writes into an invalid constant
> > address that the warning is designed to flag.
> >
> > On the assumption that those invalid addresses are deliberate,
> > the attached patch suppresses these instances by using #pragma
> > GCC diagnostic but I don't think I'm supposed to commit it (at
> > least Git won't let me).  To avoid Go bootstrap failures please
> > either apply the patch or otherwise suppress the warning (e.g.,
> > by using a volatile pointer temporary).
>
> Btw, I don't think we should diagnose things like
>
>                 *(int*)0x21 = 0x21;
>
> when somebody literally writes that he'll be just annoyed by diagnostics.
>
> Of course the above might be able to use __builtin_trap (); - it looks
> like it is placed where control flow should never end, kind of a
> __builtin_unreachable (), which means abort () might do as well.


I agree.  While this code is certainly intentional, abort will work
just as well in practice.  I committed the following to change it.

Ian

a15210699cbc60bc9ed077549dcd5288a295f42c
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index ab1384d698b..4d0f44f2dd2 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-01cb2b5e69a2d08ef3cc1ea023c22ed9b79f5114
+adcf10890833026437a94da54934ce50c0018309
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/runtime/proc.c b/libgo/runtime/proc.c
index 38bf7a6b255..3a30748d329 100644
--- a/libgo/runtime/proc.c
+++ b/libgo/runtime/proc.c
@@ -594,7 +594,7 @@ runtime_mstart(void *arg)
                gp->entry = nil;
                gp->param = nil;
                __builtin_call_with_static_chain(pfn(gp1), fv);
-               *(int*)0x21 = 0x21;
+               abort();
        }
 
        if(mp->exiting) {
@@ -662,7 +662,7 @@ setGContext(void)
                gp->entry = nil;
                gp->param = nil;
                __builtin_call_with_static_chain(pfn(gp1), fv);
-               *(int*)0x22 = 0x22;
+               abort();
        }
 }
 
diff --git a/libgo/runtime/runtime_c.c b/libgo/runtime/runtime_c.c
index 18222c14465..bc920a5d406 100644
--- a/libgo/runtime/runtime_c.c
+++ b/libgo/runtime/runtime_c.c
@@ -116,7 +116,7 @@ runtime_signalstack(byte *p, uintptr n)
        if(p == nil)
                st.ss_flags = SS_DISABLE;
        if(sigaltstack(&st, nil) < 0)
-               *(int *)0xf1 = 0xf1;
+               abort();
 }
 
 int32 go_open(char *, int32, int32)