[PATCH 1/1] mingw: enable stack smashing protector

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

To reduce Git for Windows' attack surface, we started using the Address
Space Layout Randomization and Data Execution Prevention features in
ce6a158561f9 (mingw: enable DEP and ASLR, 2019-05-08).

To remove yet another attack vector, let's make use of gcc's stack
smashing protector that helps detect stack buffer overruns early.

Rather than using -fstack-protector, we use -fstack-protector-strong
because on Windows: The latter appears to strike a better balance
between the performance impact and the provided safety.

In a non-scientific test (time git log --grep=is -p), best of 5 timings
went from 23.009s to 22.997s, i.e. the performance impact was *well*
lost in the noise.

This fixes https://github.com/git-for-windows/git/issues/501

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 config.mak.uname | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/config.mak.uname b/config.mak.uname
index b71688eeb7..2400e7879c 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -596,7 +596,8 @@ else
 			BASIC_LDFLAGS += -Wl,--large-address-aware
 		endif
 		CC = gcc
-		COMPAT_CFLAGS += -D__USE_MINGW_ANSI_STDIO=0 -DDETECT_MSYS_TTY
+		COMPAT_CFLAGS += -D__USE_MINGW_ANSI_STDIO=0 -DDETECT_MSYS_TTY \
+			-fstack-protector-strong
 		EXTLIBS += -lntdll
 		INSTALL = /bin/install
 		NO_R_TO_GCC_LINKER = YesPlease
-- 
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