cccl: Ignore -fno-strict-aliasing.

[cascardo/ovs.git] / CodingStyle

diff --git a/CodingStyle b/CodingStyle
index ce97258..d1ef65b 100644 (file)
--- a/CodingStyle
+++ b/CodingStyle
@@ -428,12 +428,10 @@ prints 255 but printf("%u", -1) prints 4294967295.
 network protocol fields or in other circumstances where the exact
 format is important.
 
-  Declare bit-fields to be type "unsigned int" or "signed int".  Do
-*not* declare bit-fields of type "int": C89 allows these to be either
-signed or unsigned according to the compiler's whim.  (A 1-bit
-bit-field of type "int" may have a range of -1...0!)  Do not declare
-bit-fields of type _Bool or enum or any other type, because these are
-not portable.
+  Declare bit-fields to be signed or unsigned integer types or _Bool
+(aka bool).  Do *not* declare bit-fields of type "int": C99 allows
+these to be either signed or unsigned according to the compiler's
+whim.  (A 1-bit bit-field of type "int" may have a range of -1...0!)
 
   Try to order structure members such that they pack well on a system
 with 2-byte "short", 4-byte "int", and 4- or 8-byte "long" and pointer
@@ -543,6 +541,11 @@ C DIALECT
     * bool and <stdbool.h>, but don't assume that bool or _Bool can
       only take on the values 0 or 1, because this behavior can't be
       simulated on C89 compilers.
+      Also, don't assume that a conversion to bool or _Bool follows
+      C99 semantics.  I.e. use "(bool)(some_value != 0)" rather than
+      "(bool)some_value".  The latter might produce unexpected results
+      on non-C99 environments.  For example, if bool is implemented as
+      a typedef of char and some_value = 0x10000000.
 
     * Designated initializers (e.g. "struct foo foo = {.a = 1};" and
       "int a[] = {[2] = 5};").