From 933e701dac1936c6f15c765b5687fbc623464ec7 Mon Sep 17 00:00:00 2001
From: Mike Sperber <sperber@deinprogramm.de>
Date: Thu, 22 Mar 2012 18:00:31 +0100
Subject: Unbreak floating point on middle-endian machines.

On some ARMs (and maybe other platforms), doubles are stored with the
the two 32-bit words reversed with respect to more common
architectures.

The symptom is this:

> io_lib:write(1.0).
"0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005299808824"

Detect that and account for it when decoding floats.
---
 erts/emulator/beam/erl_bits.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'erts/emulator')

diff --git a/erts/emulator/beam/erl_bits.c b/erts/emulator/beam/erl_bits.c
index 6f7309f493..b7c82935ff 100644
--- a/erts/emulator/beam/erl_bits.c
+++ b/erts/emulator/beam/erl_bits.c
@@ -1005,8 +1005,13 @@ erts_new_bs_put_float(Process *c_p, Eterm arg, Uint num_bits, int flags)
 
 	    if (is_float(arg)) {
 		FloatDef *fdp = (FloatDef*)(float_val(arg) + 1);
+#ifdef DOUBLE_MIDDLE_ENDIAN
+		a = fdp->fw[1];
+		b = fdp->fw[0];
+#else
 		a = fdp->fw[0];
 		b = fdp->fw[1];
+#endif
 	    } else if (is_small(arg)) {
 		u.f64 = (double) signed_val(arg);
 		a = u.i32[0];
@@ -1015,8 +1020,13 @@ erts_new_bs_put_float(Process *c_p, Eterm arg, Uint num_bits, int flags)
 		if (big_to_double(arg, &u.f64) < 0) {
 		    return 0;
 		}
+#ifdef DOUBLE_MIDDLE_ENDIAN
+		a = u.i32[1];
+		b = u.i32[0];
+#else
 		a = u.i32[0];
 		b = u.i32[1];
+#endif
 	    } else {
 		return 0;
 	    }
-- 
cgit v1.2.3


From cab9edd0a6f1fad2c3ec9661b39627756ad9d2ba Mon Sep 17 00:00:00 2001
From: Mike Sperber <sperber@deinprogramm.de>
Date: Tue, 17 Jul 2012 10:03:49 +0200
Subject: Add test for floating-point output to float_SUITE.

This catches endianness problems, such as recently reported for ARMs.
---
 erts/emulator/test/float_SUITE.erl | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

(limited to 'erts/emulator')

diff --git a/erts/emulator/test/float_SUITE.erl b/erts/emulator/test/float_SUITE.erl
index 8e6923ce9f..abe01bf5ec 100644
--- a/erts/emulator/test/float_SUITE.erl
+++ b/erts/emulator/test/float_SUITE.erl
@@ -25,7 +25,7 @@
 	 init_per_group/2,end_per_group/2,
 	 init_per_testcase/2,end_per_testcase/2,
 	 fpe/1,fp_drv/1,fp_drv_thread/1,denormalized/1,match/1,
-	 bad_float_unpack/1,cmp_zero/1, cmp_integer/1, cmp_bignum/1]).
+	 bad_float_unpack/1, write/1, cmp_zero/1, cmp_integer/1, cmp_bignum/1]).
 -export([otp_7178/1]).
 -export([hidden_inf/1]).
 
@@ -42,7 +42,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     [fpe, fp_drv, fp_drv_thread, otp_7178, denormalized,
-     match, bad_float_unpack, {group, comparison}
+     match, bad_float_unpack, write, {group, comparison}
      ,hidden_inf
     ].
 
@@ -190,6 +190,11 @@ bad_float_unpack(Config) when is_list(Config) ->
 bad_float_unpack_match(<<F:64/float>>) -> F;
 bad_float_unpack_match(<<I:64/integer-signed>>) -> I.
 
+%% Exposes endianness issues.
+
+write(Config) when is_list(Config) ->
+    "1.0" = io_lib:write(1.0).
+
 cmp_zero(_Config) ->
     cmp(0.5e-323,0).
 
-- 
cgit v1.2.3