File 0557-beam_disasm-Decode-field-flags.patch of Package erlang

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File 0557-beam_disasm-Decode-field-flags.patch of Package erlang (Revision 6832f5e4e38a54c9f251889401943f35)

Currently displaying revision 6832f5e4e38a54c9f251889401943f35 , Show latest

From ba564849ba257e1910dbbe6d01d327b925d674be Mon Sep 17 00:00:00 2001
From: Michael Davis <mcarsondavis@gmail.com>
Date: Fri, 28 Oct 2022 16:38:34 -0500
Subject: [PATCH] beam_disasm: Decode field flags

`beam_validator:bs_integer_type/2` expects field flags to be a list of
atoms (little, signed, native, etc.). This change reverses the bitflag
encoding done in `beam_asm:flag_to_bit/1` and `beam_asm:encode_arg/2`
to decode the field flags in `beam_disasm` as `beam_validator` expects.
---
 lib/compiler/src/beam_disasm.erl | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/lib/compiler/src/beam_disasm.erl b/lib/compiler/src/beam_disasm.erl
index 73207922cb..fbe8845858 100644
--- a/lib/compiler/src/beam_disasm.erl
+++ b/lib/compiler/src/beam_disasm.erl
@@ -1209,13 +1209,20 @@ resolve_arg_unsigned({u,N}) when is_integer(N), N >= 0 -> N.
 resolve_arg_integer({i,N}) when is_integer(N) -> {integer,N}.
 
 %%-----------------------------------------------------------------------
-%% The purpose of the following is just to add a hook for future changes.
-%% Currently, field flags are numbers 1-2-4-8 and only two of these
-%% numbers (BSF_LITTLE 2 -- BSF_SIGNED 4) have a semantic significance;
-%% others are just hints for speeding up the execution; see "erl_bits.h".
+%% Decodes field flags within bitstrings such as `Var/signed' or
+%% `Var/little'. This is the opposite of `beam_asm:flag_to_bit/1'.
+%% Also see "erl_bits.h".
 %%-----------------------------------------------------------------------
 
-decode_field_flags(FF) ->
+decode_field_flags(0) ->
+    {field_flags,[]};
+decode_field_flags(FieldFlags) when is_integer(FieldFlags) ->
+    FF = lists:filter(
+           fun
+               (little) -> (FieldFlags band 16#02) == 16#02;
+               (signed) -> (FieldFlags band 16#04) == 16#04;
+               (native) -> (FieldFlags band 16#10) == 16#10
+           end, [little, signed, native]),
     {field_flags,FF}.
 
 %%-----------------------------------------------------------------------
-- 
2.35.3

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File 0557-beam_disasm-Decode-field-flags.patch of Package erlang (Revision 6832f5e4e38a54c9f251889401943f35)

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