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From 3c848f2fbde81db336ec97d9be7a5a4a05015eef Mon Sep 17 00:00:00 2001
From: Ariadne Conill <ariadne@dereferenced.org>
Date: Fri, 21 Aug 2020 06:46:22 +0000
Subject: [PATCH] Turn on -D_FORTIFY_SOURCE=2 by default for C, C++, ObjC,
ObjC++, if the optimization level is > 0
---
gcc/c-family/c-cppbuiltin.c | 4 ++++
gcc/doc/invoke.texi | 6 ++++++
2 files changed, 10 insertions(+)
diff --git a/gcc/c-family/c-cppbuiltin.c b/gcc/c-family/c-cppbuiltin.c
index db91a36794a..ed976c71404 100644
--- a/gcc/c-family/c-cppbuiltin.c
+++ b/gcc/c-family/c-cppbuiltin.c
@@ -1385,6 +1385,10 @@ c_cpp_builtins (cpp_reader *pfile)
builtin_define_with_value ("__REGISTER_PREFIX__", REGISTER_PREFIX, 0);
builtin_define_with_value ("__USER_LABEL_PREFIX__", user_label_prefix, 0);
+ /* Fortify Source enabled by default for optimization levels > 0 */
+ if (optimize)
+ builtin_define_with_int_value ("_FORTIFY_SOURCE", 2);
+
/* Misc. */
if (flag_gnu89_inline)
cpp_define (pfile, "__GNUC_GNU_INLINE__");
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 17d371ef432..fe793ac08db 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -9230,6 +9230,12 @@ also turns on the following optimization flags:
Please note the warning under @option{-fgcse} about
invoking @option{-O2} on programs that use computed gotos.
+NOTE: In Alpine Linux, @option{-D_FORTIFY_SOURCE=2} is
+set by default, and is activated when @option{-O} is set to 2 or higher.
+This enables additional compile-time and run-time checks for several libc
+functions. To disable, specify either @option{-U_FORTIFY_SOURCE} or
+@option{-D_FORTIFY_SOURCE=0}.
+
@item -O3
@opindex O3
Optimize yet more. @option{-O3} turns on all optimizations specified
--
2.31.1
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