From f43834aba2ed9f8f69d961a6554bc81ecaa98f08 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Thu, 21 May 2020 11:27:09 +1000
Subject: py/py.mk: Use additional CFLAGS to compile string0.c.

Otherwise functions like memset might get optimised to call themselves (eg
with gcc 10).  And provide CFLAGS_BUILTIN so these options can be changed
by a port if needed.

Fixes issue #6053.
---
 py/py.mk | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'py')

diff --git a/py/py.mk b/py/py.mk
index 3cb505920..3e1d7989f 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -346,6 +346,11 @@ $(HEADER_BUILD)/qstrdefs.generated.h: $(PY_SRC)/makeqstrdata.py $(HEADER_BUILD)/
 
 $(PY_BUILD)/qstr.o: $(HEADER_BUILD)/qstrdefs.generated.h
 
+# Standard C functions like memset need to be compiled with special flags so
+# the compiler does not optimise these functions in terms of themselves.
+CFLAGS_BUILTIN ?= -ffreestanding -fno-builtin -fno-lto
+$(BUILD)/lib/libc/string0.o: CFLAGS += $(CFLAGS_BUILTIN)
+
 # Force nlr code to always be compiled with space-saving optimisation so
 # that the function preludes are of a minimal and predictable form.
 $(PY_BUILD)/nlr%.o: CFLAGS += -Os
-- 
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