From 07a446e7f869f79104bcc1d6accdc462e7bf7ba5 Mon Sep 17 00:00:00 2001

From: Laszlo Ersek <lersek@redhat.com>

Date: Fri, 2 Mar 2018 19:09:23 +0100

Subject: [PATCH 2/3] BaseTools/header.makefile: add "-Wno-restrict"

gcc-8 (which is part of Fedora 28) enables the new warning

"-Wrestrict" in "-Wall". This warning is documented in detail

at <https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html>; the

introduction says

> Warn when an object referenced by a restrict-qualified parameter (or, in

> C++, a __restrict-qualified parameter) is aliased by another argument,

> or when copies between such objects overlap.

It breaks the BaseTools build (in the Brotli compression library) with:

> In function 'ProcessCommandsInternal',

>     inlined from 'ProcessCommands' at dec/decode.c:1828:10:

> dec/decode.c:1781:9: error: 'memcpy' accessing between 17 and 2147483631

> bytes at offsets 16 and 16 overlaps between 17 and 2147483631 bytes at

> offset 16 [-Werror=restrict]

>          memcpy(copy_dst + 16, copy_src + 16, (size_t)(i - 16));

>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> In function 'ProcessCommandsInternal',

>     inlined from 'SafeProcessCommands' at dec/decode.c:1833:10:

> dec/decode.c:1781:9: error: 'memcpy' accessing between 17 and 2147483631

> bytes at offsets 16 and 16 overlaps between 17 and 2147483631 bytes at

> offset 16 [-Werror=restrict]

>          memcpy(copy_dst + 16, copy_src + 16, (size_t)(i - 16));

>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Paolo Bonzini <pbonzini@redhat.com> analyzed the Brotli source in detail,

and concluded that the warning is a false positive:

> This seems safe to me, because it's preceded by:

>

>     uint8_t* copy_dst = &s->ringbuffer[pos];

>     uint8_t* copy_src = &s->ringbuffer[src_start];

>     int dst_end = pos + i;

>     int src_end = src_start + i;

>     if (src_end > pos && dst_end > src_start) {

>       /* Regions intersect. */

>       goto CommandPostWrapCopy;

>     }

>

> If [src_start, src_start + i) and [pos, pos + i) don't intersect, then

> neither do [src_start + 16, src_start + i) and [pos + 16, pos + i).

>

> The if seems okay:

>

>        (src_start + i > pos && pos + i > src_start)

>

> which can be rewritten to:

>

>        (pos < src_start + i && src_start < pos + i)

>

> Then the numbers are in one of these two orders:

>

>      pos <= src_start < pos + i <= src_start + i

>      src_start <= pos < src_start + i <= pos + i

>

> These two would be allowed by the "if", but they can only happen if pos

> == src_start so they degenerate to the same two orders above:

>

>      pos <= src_start < src_start + i <= pos + i

>      src_start <= pos < pos + i <= src_start + i

>

> So it is a false positive in GCC.

Disable the warning for now.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Cc: Cole Robinson <crobinso@redhat.com>

Cc: Liming Gao <liming.gao@intel.com>

Cc: Paolo Bonzini <pbonzini@redhat.com>

Cc: Yonghong Zhu <yonghong.zhu@intel.com>

Reported-by: Cole Robinson <crobinso@redhat.com>

Contributed-under: TianoCore Contribution Agreement 1.1

Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Message-Id: <20180302180924.4312-3-lersek@redhat.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

---

 BaseTools/Source/C/Makefiles/header.makefile | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/BaseTools/Source/C/Makefiles/header.makefile b/BaseTools/Source/C/Makefiles/header.makefile

index 6c3826aecb..3feae10095 100644

--- a/BaseTools/Source/C/Makefiles/header.makefile

+++ b/BaseTools/Source/C/Makefiles/header.makefile

@@ -47,9 +47,9 @@ INCLUDE = $(TOOL_INCLUDE) -I $(MAKEROOT) -I $(MAKEROOT)/Include/Common -I $(MAKE

 BUILD_CPPFLAGS = $(INCLUDE) -O2

 ifeq ($(DARWIN),Darwin)

 # assume clang or clang compatible flags on OS X

-BUILD_CFLAGS = -MD -fshort-wchar -fno-strict-aliasing -Wall -Werror -Wno-deprecated-declarations -Wno-stringop-truncation -Wno-self-assign -Wno-unused-result -nostdlib -c -g

+BUILD_CFLAGS = -MD -fshort-wchar -fno-strict-aliasing -Wall -Werror -Wno-deprecated-declarations -Wno-stringop-truncation -Wno-restrict -Wno-self-assign -Wno-unused-result -nostdlib -c -g

 else

-BUILD_CFLAGS = -MD -fshort-wchar -fno-strict-aliasing -Wall -Werror -Wno-deprecated-declarations -Wno-stringop-truncation -Wno-unused-result -nostdlib -c -g

+BUILD_CFLAGS = -MD -fshort-wchar -fno-strict-aliasing -Wall -Werror -Wno-deprecated-declarations -Wno-stringop-truncation -Wno-restrict -Wno-unused-result -nostdlib -c -g

 endif

 BUILD_LFLAGS =

 BUILD_CXXFLAGS = -Wno-unused-result

-- 

2.14.3