Add syntax in try/catch to retrieve the stacktrace directly

This commit adds a new syntax for retrieving the stacktrace
without calling erlang:get_stacktrace/0. That allow us to
deprecate erlang:get_stacktrace/0 and ultimately remove it.

The problem with erlang:get_stacktrace/0 is that it can keep huge
terms in a process for an indefinite time after an exception. The
stacktrace can be huge after a 'function_clause' exception or a failed
call to a BIF or operator, because the arguments for the call will be
included in the stacktrace. For example:

1> catch abs(lists:seq(1, 1000)).
{'EXIT',{badarg,[{erlang,abs,
                         [[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20|...]],
                         []},
                 {erl_eval,do_apply,6,[{file,"erl_eval.erl"},{line,674}]},
                 {erl_eval,expr,5,[{file,"erl_eval.erl"},{line,431}]},
                 {shell,exprs,7,[{file,"shell.erl"},{line,687}]},
                 {shell,eval_exprs,7,[{file,"shell.erl"},{line,642}]},
                 {shell,eval_loop,3,[{file,"shell.erl"},{line,627}]}]}}
2> erlang:get_stacktrace().
[{erlang,abs,
         [[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,
           23,24|...]],
         []},
 {erl_eval,do_apply,6,[{file,"erl_eval.erl"},{line,674}]},
 {erl_eval,expr,5,[{file,"erl_eval.erl"},{line,431}]},
 {shell,exprs,7,[{file,"shell.erl"},{line,687}]},
 {shell,eval_exprs,7,[{file,"shell.erl"},{line,642}]},
 {shell,eval_loop,3,[{file,"shell.erl"},{line,627}]}]
3>

We can extend the syntax for clauses in try/catch to optionally bind
the stacktrace to a variable.

Here is an example using the current syntax:

    try
      Expr
    catch C:E ->
      Stk = erlang:get_stacktrace(),
      .
      .
      .

In the new syntax, it would look like:

    try
      Expr
    catch
      C:E:Stk ->
       .
       .
       .

Only a variable (not a pattern) is allowed in the stacktrace position,
to discourage matching of the stacktrace. (Matching would also be
expensive, because the raw format of the stacktrace would have to be
converted to the cooked form before matching.)

Note that:

    try
      Expr
    catch E ->
      .
      .
      .

is a shorthand for:

    try
      Expr
    catch throw:E ->
      .
      .
      .

If the stacktrace is to be retrieved for a throw, the 'throw:'
prefix must be explicitly included:

    try
      Expr
    catch throw:E:Stk ->
      .
      .
      .

7 files changed, 22 insertions, 0 deletions

diff --git a/erts/emulator/beam/instrs.tab b/erts/emulator/beam/instrs.tab
index c17d1a8f69..f4acf6167d 100644
--- a/erts/emulator/beam/instrs.tab
+++ b/erts/emulator/beam/instrs.tab
@@ -924,3 +924,8 @@ i_raise() {
     //| -no_next
 }
 
+build_stacktrace() {
+    SWAPOUT;
+    x(0) = build_stacktrace(c_p, x(0));
+    SWAPIN;
+}
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 3df91056cb..ba4ca67e5e 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1575,3 +1575,9 @@ i_recv_mark
 recv_set Fail | label Lbl | loop_rec Lf Reg => \
    i_recv_set | label Lbl | loop_rec Lf Reg
 i_recv_set
+
+#
+# OTP 21.
+#
+
+build_stacktrace
diff --git a/erts/emulator/hipe/hipe_bif2.c b/erts/emulator/hipe/hipe_bif2.c
index 9ebbb22846..df377b2153 100644
--- a/erts/emulator/hipe/hipe_bif2.c
+++ b/erts/emulator/hipe/hipe_bif2.c
@@ -190,3 +190,8 @@ BIF_RETTYPE hipe_bifs_llvm_fix_pinned_regs_0(BIF_ALIST_0)
 {
     BIF_RET(am_ok);
 }
+
+BIF_RETTYPE hipe_bifs_build_stacktrace_1(BIF_ALIST_1)
+{
+    BIF_RET(build_stacktrace(BIF_P, BIF_ARG_1));
+}
diff --git a/erts/emulator/hipe/hipe_bif2.tab b/erts/emulator/hipe/hipe_bif2.tab
index bbcb577be0..c4da44606a 100644
--- a/erts/emulator/hipe/hipe_bif2.tab
+++ b/erts/emulator/hipe/hipe_bif2.tab
@@ -32,3 +32,4 @@ bif hipe_bifs:modeswitch_debug_on/0
 bif hipe_bifs:modeswitch_debug_off/0
 bif hipe_bifs:debug_native_called/2
 bif hipe_bifs:llvm_fix_pinned_regs/0
+bif hipe_bifs:build_stacktrace/1
diff --git a/erts/emulator/hipe/hipe_bif_list.m4 b/erts/emulator/hipe/hipe_bif_list.m4
index 625d8486fd..4f0a655508 100644
--- a/erts/emulator/hipe/hipe_bif_list.m4
+++ b/erts/emulator/hipe/hipe_bif_list.m4
@@ -186,6 +186,7 @@ gc_bif_interface_1(nbif_erase_1, erase_1)
 gc_bif_interface_1(nbif_erts_internal_garbage_collect_1, erts_internal_garbage_collect_1)
 gc_nofail_primop_interface_1(nbif_gc_1, hipe_gc)
 gc_bif_interface_2(nbif_put_2, put_2)
+gc_bif_interface_2(nbif_hipe_bifs_build_stacktrace, hipe_bifs_build_stacktrace_1)
 
 /*
  * Debug BIFs that need read access to the full state.
diff --git a/erts/emulator/hipe/hipe_native_bif.h b/erts/emulator/hipe/hipe_native_bif.h
index d5081b8438..6dffec1d8d 100644
--- a/erts/emulator/hipe/hipe_native_bif.h
+++ b/erts/emulator/hipe/hipe_native_bif.h
@@ -104,6 +104,9 @@ void hipe_emulate_fpe(Process*);
 AEXTERN(void,nbif_emasculate_binary,(Eterm));
 void hipe_emasculate_binary(Eterm);
 
+AEXTERN(BIF_RETTYPE,nbif_hipe_bifs_build_stacktrace,(Process*,Eterm));
+BIF_RETTYPE hipe_bifs_build_stacktrace_1(BIF_ALIST_1);
+
 /*
  * Stuff that is different in SMP and non-SMP.
  */
diff --git a/erts/emulator/hipe/hipe_primops.h b/erts/emulator/hipe/hipe_primops.h
index a6abd3e011..d6fd10bdff 100644
--- a/erts/emulator/hipe/hipe_primops.h
+++ b/erts/emulator/hipe/hipe_primops.h
@@ -83,6 +83,7 @@ PRIMOP_LIST(am_emulate_fpe, &nbif_emulate_fpe)
 #endif
 PRIMOP_LIST(am_emasculate_binary, &nbif_emasculate_binary)
 PRIMOP_LIST(am_debug_native_called, &nbif_hipe_bifs_debug_native_called)
+PRIMOP_LIST(am_build_stacktrace, &nbif_hipe_bifs_build_stacktrace)
 
 #if defined(__sparc__)
 #include "hipe_sparc_primops.h"