[OpenJDK 2D-Dev] Fwd: [PATCH] Fix compiler warnings with newer GCC 7.2.1

[Alan Bateman]

This was sent to core-libs-dev, I assume it was meant for 2d-dev and 
serviceability-dev.

-------- Forwarded Message --------
Subject:        [PATCH] Fix compiler warnings with newer GCC 7.2.1
Date:   Fri, 2 Feb 2018 16:12:08 -0800
From:   Indu Bhagat <indu.bha...@oracle.com>
To:     core-libs-...@openjdk.java.net



This patch fixes a few of the compiler warnings when using gcc 7.2.1.

In general there are many other warnings (a majority of which are implicit 
fallthrough warnings in jdk.crypto.ec package's ecp_*.c files and java.desktop 
package's splashscreen_gfx_impl.h file).
I can post them if there is interest.
Most warnings, however, look benign (modulo some warnings about unintialized 
access that I cannot comment on; they need that the code be thoroughly 
understood).
libfdlibm misleading indentation warnings are already 
knownhttp://mail.openjdk.java.net/pipermail/jdk9-dev/2016-June/004494.html

Thanks

----------------------------------------------
The patch fixes the following warnings :

1. 
<jdk-dev>/jdk/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c: 
In function ‘mask_s2u’:
   
<jdk-dev>/jdk/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c:389:22:
 warning: left shift of negative value [-Wshift-negative-value]
     *mask = htonl(-1 << (32 - m));
                      ^
2. <jdk-dev>/jdk/src/java.desktop/share/native/libjavajpeg/jdphuff.c: In 
function ‘decode_mcu_AC_refine’:
   <jdk-dev>/jdk/src/java.desktop/share/native/libjavajpeg/jdphuff.c:505:17: 
warning: left shift of negative value [-Wshift-negative-value]
   int m1 = (-1) << cinfo->Al;   /* -1 in the bit position being coded*/
                 ^~
3. 
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:
 In function ‘void position_mark(const hb_ot_shape_plan_t*, hb_font_t*, hb_buffer_t*, 
hb_glyph_extents_t&, unsigned int, unsigned int)’:
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:223:14:
 warning: this statement may fall through [-Wimplicit-fallthrough=]
       } else if (buffer->props.direction == HB_DIRECTION_RTL) {
              ^~
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:229:5:
 note: here
     default:
     ^~~~~~~
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:261:27:
 warning: this statement may fall through [-Wimplicit-fallthrough=]
       base_extents.height -= y_gap;
       ~~~~~~~~~~~~~~~~~~~~^~~~~~~~
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:264:5:
 note: here
     case HB_UNICODE_COMBINING_CLASS_ATTACHED_BELOW_LEFT:
     ^~~~
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:282:27:
 warning: this statement may fall through [-Wimplicit-fallthrough=]
       base_extents.height -= y_gap;
       ~~~~~~~~~~~~~~~~~~~~^~~~~~~~
   
<jdk-dev>/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-ot-shape-fallback.cc:285:5:
 note: here
     case HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE:
     ^~~~
-----------

diff --git 
a/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-private.hh 
b/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-private.hh
--- a/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-private.hh
+++ b/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-private.hh
@@ -158,6 +158,9 @@
     */
 #  include <sal.h>
 #  define HB_FALLTHROUGH __fallthrough
+#elif __GNUC__ >= 7
+   /* GNU fallthrough attribute is available from GCC7 */
+#  define HB_FALLTHROUGH __attribute__((fallthrough))
 #else
 #  define HB_FALLTHROUGH /* FALLTHROUGH */
 #endif
diff --git a/src/java.desktop/share/native/libjavajpeg/jdphuff.c 
b/src/java.desktop/share/native/libjavajpeg/jdphuff.c
--- a/src/java.desktop/share/native/libjavajpeg/jdphuff.c
+++ b/src/java.desktop/share/native/libjavajpeg/jdphuff.c
@@ -501,8 +501,10 @@
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int Se = cinfo->Se;
-  int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
-  int m1 = (-1) << cinfo->Al;   /* -1 in the bit position being coded */
+  /* 1 in the bit position being coded */
+  int p1 = 1 << cinfo->Al;
+  /* -1 in the bit position being coded */
+  int m1 = (int)((unsigned)(~0) << cinfo->Al);
   register int s, k, r;
   unsigned int EOBRUN;
   JBLOCKROW block;
diff --git a/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c 
b/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c
--- a/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c
+++ b/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c
@@ -386,7 +386,7 @@
        return instr;
     }
 
-    *mask = htonl(-1 << (32 - m));
+    *mask = htonl((uint32_t)(~0) << (32 - m));
     return s;
 }