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author | Allan Sandfeld Jensen <allan.jensen@theqtcompany.com> | 2016-01-25 11:39:07 +0100 |
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committer | Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com> | 2016-01-25 15:20:42 +0000 |
commit | 6c91641271e536ffaa88a1dff5127e42ee99a91e (patch) | |
tree | 703d9dd49602377ddc90cbf886aad37913f2496b /chromium/base/macros.h | |
parent | b145b7fafd36f0c260d6a768c81fc14e32578099 (diff) | |
download | qtwebengine-chromium-6c91641271e536ffaa88a1dff5127e42ee99a91e.tar.gz |
BASELINE: Update Chromium to 49.0.2623.23
Also adds missing printing sources.
Change-Id: I3726b8f0c7d6751c9fc846096c571fadca7108cd
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Diffstat (limited to 'chromium/base/macros.h')
-rw-r--r-- | chromium/base/macros.h | 98 |
1 files changed, 5 insertions, 93 deletions
diff --git a/chromium/base/macros.h b/chromium/base/macros.h index c5f503fbc3a..46ee1dadb47 100644 --- a/chromium/base/macros.h +++ b/chromium/base/macros.h @@ -11,7 +11,6 @@ #define BASE_MACROS_H_ #include <stddef.h> // For size_t. -#include <string.h> // For memcpy. // Put this in the declarations for a class to be uncopyable. #define DISALLOW_COPY(TypeName) \ @@ -27,13 +26,6 @@ TypeName(const TypeName&); \ void operator=(const TypeName&) -// An older, deprecated, politically incorrect name for the above. -// NOTE: The usage of this macro was banned from our code base, but some -// third_party libraries are yet using it. -// TODO(tfarina): Figure out how to fix the usage of this macro in the -// third_party libraries and get rid of it. -#define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName) - // A macro to disallow all the implicit constructors, namely the // default constructor, copy constructor and operator= functions. // @@ -44,10 +36,11 @@ TypeName() = delete; \ DISALLOW_COPY_AND_ASSIGN(TypeName) -// The arraysize(arr) macro returns the # of elements in an array arr. -// The expression is a compile-time constant, and therefore can be -// used in defining new arrays, for example. If you use arraysize on -// a pointer by mistake, you will get a compile-time error. +// The arraysize(arr) macro returns the # of elements in an array arr. The +// expression is a compile-time constant, and therefore can be used in defining +// new arrays, for example. If you use arraysize on a pointer by mistake, you +// will get a compile-time error. For the technical details, refer to +// http://blogs.msdn.com/b/the1/archive/2004/05/07/128242.aspx. // This template function declaration is used in defining arraysize. // Note that the function doesn't need an implementation, as we only @@ -55,87 +48,6 @@ template <typename T, size_t N> char (&ArraySizeHelper(T (&array)[N]))[N]; #define arraysize(array) (sizeof(ArraySizeHelper(array))) -// The COMPILE_ASSERT macro can be used to verify that a compile time -// expression is true. For example, you could use it to verify the -// size of a static array: -// -// COMPILE_ASSERT(arraysize(content_type_names) == CONTENT_NUM_TYPES, -// content_type_names_incorrect_size); -// -// or to make sure a struct is smaller than a certain size: -// -// COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); -// -// The second argument to the macro is the name of the variable. If -// the expression is false, most compilers will issue a warning/error -// containing the name of the variable. - -#undef COMPILE_ASSERT -#define COMPILE_ASSERT(expr, msg) static_assert(expr, #msg) - -// bit_cast<Dest,Source> is a template function that implements the -// equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in -// very low-level functions like the protobuf library and fast math -// support. -// -// float f = 3.14159265358979; -// int i = bit_cast<int32>(f); -// // i = 0x40490fdb -// -// The classical address-casting method is: -// -// // WRONG -// float f = 3.14159265358979; // WRONG -// int i = * reinterpret_cast<int*>(&f); // WRONG -// -// The address-casting method actually produces undefined behavior -// according to ISO C++ specification section 3.10 -15 -. Roughly, this -// section says: if an object in memory has one type, and a program -// accesses it with a different type, then the result is undefined -// behavior for most values of "different type". -// -// This is true for any cast syntax, either *(int*)&f or -// *reinterpret_cast<int*>(&f). And it is particularly true for -// conversions between integral lvalues and floating-point lvalues. -// -// The purpose of 3.10 -15- is to allow optimizing compilers to assume -// that expressions with different types refer to different memory. gcc -// 4.0.1 has an optimizer that takes advantage of this. So a -// non-conforming program quietly produces wildly incorrect output. -// -// The problem is not the use of reinterpret_cast. The problem is type -// punning: holding an object in memory of one type and reading its bits -// back using a different type. -// -// The C++ standard is more subtle and complex than this, but that -// is the basic idea. -// -// Anyways ... -// -// bit_cast<> calls memcpy() which is blessed by the standard, -// especially by the example in section 3.9 . Also, of course, -// bit_cast<> wraps up the nasty logic in one place. -// -// Fortunately memcpy() is very fast. In optimized mode, with a -// constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline -// code with the minimal amount of data movement. On a 32-bit system, -// memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8) -// compiles to two loads and two stores. -// -// I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1. -// -// WARNING: if Dest or Source is a non-POD type, the result of the memcpy -// is likely to surprise you. - -template <class Dest, class Source> -inline Dest bit_cast(const Source& source) { - COMPILE_ASSERT(sizeof(Dest) == sizeof(Source), VerifySizesAreEqual); - - Dest dest; - memcpy(&dest, &source, sizeof(dest)); - return dest; -} - // Used to explicitly mark the return value of a function as unused. If you are // really sure you don't want to do anything with the return value of a function // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: |