[PATCH v3.1 3/9] lib: Introduce macros for bit operations

diff --git a/f7/72d4c25159cc998c82d030eea54086abd72362 b/f7/72d4c25159cc998c82d030eea54086abd72362
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+From: Austin Clements <aclements@csail.mit.edu>\r
+To: notmuch@notmuchmail.org\r
+Subject: [PATCH v3.1 3/9] lib: Introduce macros for bit operations\r
+Date: Fri, 24 Oct 2014 08:49:15 -0400\r
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+Cc: Austin Clements <aclements@csail.mit.edu>\r
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+\r
+These macros help clarify basic bit-twiddling code and are written to\r
+be robust against C undefined behavior of shift operators.\r
+---\r
+ lib/message.cc        |  6 +++---\r
+ lib/notmuch-private.h | 11 +++++++++++\r
+ 2 files changed, 14 insertions(+), 3 deletions(-)\r
+\r
+diff --git a/lib/message.cc b/lib/message.cc\r
+index 38bc929..55d2ff6 100644\r
+--- a/lib/message.cc\r
++++ b/lib/message.cc\r
+@@ -869,7 +869,7 @@ notmuch_bool_t\r
+ notmuch_message_get_flag (notmuch_message_t *message,\r
+                         notmuch_message_flag_t flag)\r
+ {\r
+-    return message->flags & (1 << flag);\r
++    return NOTMUCH_TEST_BIT (message->flags, flag);\r
+ }\r
+ \r
+ void\r
+@@ -877,9 +877,9 @@ notmuch_message_set_flag (notmuch_message_t *message,\r
+                         notmuch_message_flag_t flag, notmuch_bool_t enable)\r
+ {\r
+     if (enable)\r
+-      message->flags |= (1 << flag);\r
++      NOTMUCH_SET_BIT (&message->flags, flag);\r
+     else\r
+-      message->flags &= ~(1 << flag);\r
++      NOTMUCH_CLEAR_BIT (&message->flags, flag);\r
+ }\r
+ \r
+ time_t\r
+diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h\r
+index 36cc12b..b86897c 100644\r
+--- a/lib/notmuch-private.h\r
++++ b/lib/notmuch-private.h\r
+@@ -63,6 +63,17 @@ NOTMUCH_BEGIN_DECLS\r
+ #define STRNCMP_LITERAL(var, literal) \\r
+     strncmp ((var), (literal), sizeof (literal) - 1)\r
+ \r
++/* Robust bit test/set/reset macros */\r
++#define NOTMUCH_TEST_BIT(val, bit) \\r
++    (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? 0       \\r
++     : !!((val) & (1ull << (bit))))\r
++#define NOTMUCH_SET_BIT(valp, bit) \\r
++    (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? *(valp) \\r
++     : (*(valp) |= (1ull << (bit))))\r
++#define NOTMUCH_CLEAR_BIT(valp,  bit) \\r
++    (((bit) < 0 || (bit) >= CHAR_BIT * sizeof (unsigned long long)) ? *(valp) \\r
++     : (*(valp) &= ~(1ull << (bit))))\r
++\r
+ #define unused(x) x __attribute__ ((unused))\r
+ \r
+ #ifdef __cplusplus\r
+-- \r
+2.1.0\r
+\r