fix altivec.h redefinition issue

fix #426

.travis.yml

@@ -93,10 +93,12 @@ matrix:
         - CC=powerpc-linux-gnu-gcc RUN_ENV=qemu-ppc-static LDFLAGS=-static make check   # Scalar code path
         - make clean
         - CC=powerpc64-linux-gnu-gcc RUN_ENV=qemu-ppc64-static CPPFLAGS=-DXXH_VECTOR=XXH_SCALAR CFLAGS="-O3" LDFLAGS="-static -m64" make check   # Scalar code path
-        - make clean
         # VSX code
-        - CC=powerpc64-linux-gnu-gcc RUN_ENV="qemu-ppc64-static -cpu power8" CPPFLAGS=-DXXH_VECTOR=XXH_VSX CFLAGS="-O3 -maltivec -mvsx -mcpu=power8 -mpower8-vector" LDFLAGS="-static -m64" make check   # Auto code path
         - make clean
+        - CC=powerpc64-linux-gnu-gcc RUN_ENV="qemu-ppc64-static -cpu power8" CPPFLAGS=-DXXH_VECTOR=XXH_VSX CFLAGS="-O3 -maltivec -mvsx -mcpu=power8 -mpower8-vector" LDFLAGS="-static -m64" make check   # VSX code path
+        # altivec.h redefinition issue #426
+        - make clean
+        - CC=powerpc64-linux-gnu-gcc CPPFLAGS=-DXXH_VECTOR=XXH_VSX CFLAGS="-maltivec -mvsx -mcpu=power8 -mpower8-vector" make -C tests test_ppc_redefine
 
     - name: PPC64LE compilation and consistency checks
       dist: xenial
@@ -107,6 +109,9 @@ matrix:
         # VSX code path (64-bit)
         - make clean
         - CPPFLAGS=-DXXH_VECTOR=XXH_VSX CFLAGS="-O3 -maltivec -mvsx -mpower8-vector -mcpu=power8" LDFLAGS="-static" make check
+        # altivec.h redefinition issue #426
+        - make clean
+        - CPPFLAGS=-DXXH_VECTOR=XXH_VSX CFLAGS="-maltivec -mvsx -mcpu=power8 -mpower8-vector" make -C tests test_ppc_redefine 
 
     - name: IBM s390x compilation and consistency checks
       dist: bionic

tests/Makefile

@@ -1,4 +1,4 @@
-CFLAGS += -Wall -Wextra -g
+CFLAGS += -Wall -Wextra -Wundef -g
 
 NM = nm
 GREP = grep
@@ -47,6 +47,11 @@ test_multiInclude:
 	# ! $(NM) multiInclude | $(GREP) TESTN_
 	#@$(MAKE) clean
 
+.PHONY: test_ppc_redefine
+test_ppc_redefine: ppc_define.c
+	@$(MAKE) clean
+	$(CC) $(CPPFLAGS) $(CFLAGS) -c $^
+
 xxhsum$(EXT): ../xxhash.c ../xxhash.h ../xxhsum.c
 	$(CC) $(CFLAGS) $(LDFLAGS) ../xxhash.c ../xxhsum.c -o $@
 

tests/ppc_define.c

@@ -0,0 +1,62 @@
+/*
+ * Multi-include test program
+ * ensure that pixel, bool and vector are not redefined
+ *
+ * Copyright (C) 2020 Yann Collet
+ *
+ * GPL v2 License
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * You can contact the author at:
+ *   - xxHash homepage: https://www.xxhash.com
+ *   - xxHash source repository: https://github.com/Cyan4973/xxHash
+ */
+
+/* gcc's altivec.h, included for the VSX code path,
+ * may, in some circumstances, redefine
+ * bool, vector and pixel keywords.
+ *
+ * This unit checks if it happens.
+ * It's a compile test.
+ * The test is mostly meaningful for PPC target using altivec.h
+ * hence XXH_VECTOR == XXH_VSX
+ */
+
+#define BOOL_VALUE 32123456
+#define bool BOOL_VALUE
+
+#define VECTOR_VALUE 374464784
+#define vector VECTOR_VALUE
+
+#define PIXEL_VALUE 5846841
+#define pixel PIXEL_VALUE
+
+#define XXH_INLINE_ALL
+#include "../xxhash.h"
+
+#if (bool != BOOL_VALUE)
+#  error "bool macro was redefined !"
+#endif
+
+#if (vector != VECTOR_VALUE)
+#  error "vector macro was redefined !"
+#endif
+
+#if (pixel != PIXEL_VALUE)
+#  error "pixel macro was redefined !"
+#endif
+
+int g_nonEmptyUnit = 0;

xxhash.h

@@ -2398,11 +2398,20 @@ XXH_PUBLIC_API XXH64_hash_t XXH64_hashFromCanonical(const XXH64_canonical_t* src
 #  if defined(__s390x__)
 #    include <s390intrin.h>
 #  else
+/* gcc's altivec.h can have the unwanted consequence to unconditionally
+ * #define bool, vector, and pixel keywords,
+ * with bad consequences for programs already using these keywords for other purposes.
+ * The paragraph defining these macros is skipped when __APPLE_ALTIVEC__ is defined.
+ * __APPLE_ALTIVEC__ is _generally_ defined automatically by the compiler,
+ * but it seems that, in some cases, it isn't.
+ * Force the build macro to be defined, so that keywords are not altered.
+ */
+#    if defined(__GNUC__) && !defined(__APPLE_ALTIVEC__)
+#      define __APPLE_ALTIVEC__
+#    endif
 #    include <altivec.h>
 #  endif
 
-#  undef vector /* Undo the pollution */
-
 typedef __vector unsigned long long xxh_u64x2;
 typedef __vector unsigned char xxh_u8x16;
 typedef __vector unsigned xxh_u32x4;