--- a/gcc/doc/implement-c.texi	Sun Aug 21 07:07:55 2011 +0900
+++ b/gcc/doc/implement-c.texi	Fri Oct 27 22:46:09 2017 +0900
@@ -1,18 +1,17 @@
-@c Copyright (C) 2001, 2002, 2003, 2004, 2006, 2008
-@c Free Software Foundation, Inc.
+@c Copyright (C) 2001-2017 Free Software Foundation, Inc.
 @c This is part of the GCC manual.
 @c For copying conditions, see the file gcc.texi.
 
 @node C Implementation
-@chapter C Implementation-defined behavior
+@chapter C Implementation-Defined Behavior
 @cindex implementation-defined behavior, C language
 
 A conforming implementation of ISO C is required to document its
 choice of behavior in each of the areas that are designated
 ``implementation defined''.  The following lists all such areas,
-along with the section numbers from the ISO/IEC 9899:1990 and ISO/IEC
-9899:1999 standards.  Some areas are only implementation-defined in
-one version of the standard.
+along with the section numbers from the ISO/IEC 9899:1990, ISO/IEC
+9899:1999 and ISO/IEC 9899:2011 standards.  Some areas are only
+implementation-defined in one version of the standard.
 
 Some choices depend on the externally determined ABI for the platform
 (including standard character encodings) which GCC follows; these are
@@ -48,14 +47,15 @@
 
 @itemize @bullet
 @item
-@cite{How a diagnostic is identified (C90 3.7, C99 3.10, C90 and C99 5.1.1.3).}
+@cite{How a diagnostic is identified (C90 3.7, C99 and C11 3.10, C90,
+C99 and C11 5.1.1.3).}
 
 Diagnostics consist of all the output sent to stderr by GCC@.
 
 @item
 @cite{Whether each nonempty sequence of white-space characters other than
 new-line is retained or replaced by one space character in translation
-phase 3 (C90 and C99 5.1.1.2).}
+phase 3 (C90, C99 and C11 5.1.1.2).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
@@ -71,7 +71,8 @@
 @itemize @bullet
 @item
 @cite{The mapping between physical source file multibyte characters
-and the source character set in translation phase 1 (C90 and C99 5.1.1.2).}
+and the source character set in translation phase 1 (C90, C99 and C11
+5.1.1.2).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
@@ -84,14 +85,14 @@
 @itemize @bullet
 @item
 @cite{Which additional multibyte characters may appear in identifiers
-and their correspondence to universal character names (C99 6.4.2).}
+and their correspondence to universal character names (C99 and C11 6.4.2).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
 
 @item
 @cite{The number of significant initial characters in an identifier
-(C90 6.1.2, C90 and C99 5.2.4.1, C99 6.4.2).}
+(C90 6.1.2, C90, C99 and C11 5.2.4.1, C99 and C11 6.4.2).}
 
 For internal names, all characters are significant.  For external names,
 the number of significant characters are defined by the linker; for
@@ -101,7 +102,7 @@
 @cite{Whether case distinctions are significant in an identifier with
 external linkage (C90 6.1.2).}
 
-This is a property of the linker.  C99 requires that case distinctions
+This is a property of the linker.  C99 and C11 require that case distinctions
 are always significant in identifiers with external linkage and
 systems without this property are not supported by GCC@.
 
@@ -112,33 +113,34 @@
 
 @itemize @bullet
 @item
-@cite{The number of bits in a byte (C90 3.4, C99 3.6).}
+@cite{The number of bits in a byte (C90 3.4, C99 and C11 3.6).}
 
 Determined by ABI@.
 
 @item
-@cite{The values of the members of the execution character set (C90
-and C99 5.2.1).}
+@cite{The values of the members of the execution character set (C90,
+C99 and C11 5.2.1).}
 
 Determined by ABI@.
 
 @item
 @cite{The unique value of the member of the execution character set produced
-for each of the standard alphabetic escape sequences (C90 and C99 5.2.2).}
+for each of the standard alphabetic escape sequences (C90, C99 and C11
+5.2.2).}
 
 Determined by ABI@.
 
 @item
 @cite{The value of a @code{char} object into which has been stored any
 character other than a member of the basic execution character set
-(C90 6.1.2.5, C99 6.2.5).}
+(C90 6.1.2.5, C99 and C11 6.2.5).}
 
 Determined by ABI@.
 
 @item
 @cite{Which of @code{signed char} or @code{unsigned char} has the same
 range, representation, and behavior as ``plain'' @code{char} (C90
-6.1.2.5, C90 6.2.1.1, C99 6.2.5, C99 6.3.1.1).}
+6.1.2.5, C90 6.2.1.1, C99 and C11 6.2.5, C99 and C11 6.3.1.1).}
 
 @opindex fsigned-char
 @opindex funsigned-char
@@ -149,23 +151,25 @@
 @item
 @cite{The mapping of members of the source character set (in character
 constants and string literals) to members of the execution character
-set (C90 6.1.3.4, C99 6.4.4.4, C90 and C99 5.1.1.2).}
+set (C90 6.1.3.4, C99 and C11 6.4.4.4, C90, C99 and C11 5.1.1.2).}
 
 Determined by ABI@.
 
 @item
 @cite{The value of an integer character constant containing more than one
 character or containing a character or escape sequence that does not map
-to a single-byte execution character (C90 6.1.3.4, C99 6.4.4.4).}
+to a single-byte execution character (C90 6.1.3.4, C99 and C11 6.4.4.4).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
 
 @item
 @cite{The value of a wide character constant containing more than one
-multibyte character, or containing a multibyte character or escape
-sequence not represented in the extended execution character set (C90
-6.1.3.4, C99 6.4.4.4).}
+multibyte character or a single multibyte character that maps to
+multiple members of the extended execution character set, or
+containing a multibyte character or escape sequence not represented in
+the extended execution character set (C90 6.1.3.4, C99 and C11
+6.4.4.4).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
@@ -174,24 +178,44 @@
 @cite{The current locale used to convert a wide character constant consisting
 of a single multibyte character that maps to a member of the extended
 execution character set into a corresponding wide character code (C90
-6.1.3.4, C99 6.4.4.4).}
+6.1.3.4, C99 and C11 6.4.4.4).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
 
 @item
+@cite{Whether differently-prefixed wide string literal tokens can be
+concatenated and, if so, the treatment of the resulting multibyte
+character sequence (C11 6.4.5).}
+
+Such tokens may not be concatenated.
+
+@item
 @cite{The current locale used to convert a wide string literal into
-corresponding wide character codes (C90 6.1.4, C99 6.4.5).}
+corresponding wide character codes (C90 6.1.4, C99 and C11 6.4.5).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
 
 @item
 @cite{The value of a string literal containing a multibyte character or escape
-sequence not represented in the execution character set (C90 6.1.4, C99 6.4.5).}
+sequence not represented in the execution character set (C90 6.1.4,
+C99 and C11 6.4.5).}
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The encoding of any of @code{wchar_t}, @code{char16_t}, and
+@code{char32_t} where the corresponding standard encoding macro
+(@code{__STDC_ISO_10646__}, @code{__STDC_UTF_16__}, or
+@code{__STDC_UTF_32__}) is not defined (C11 6.10.8.2).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.  @code{char16_t} and
+@code{char32_t} literals are always encoded in UTF-16 and UTF-32
+respectively.
+
 @end itemize
 
 @node Integers implementation
@@ -199,7 +223,8 @@
 
 @itemize @bullet
 @item
-@cite{Any extended integer types that exist in the implementation (C99 6.2.5).}
+@cite{Any extended integer types that exist in the implementation (C99
+and C11 6.2.5).}
 
 GCC does not support any extended integer types.
 @c The __mode__ attribute might create types of precisions not
@@ -212,14 +237,14 @@
 @item
 @cite{Whether signed integer types are represented using sign and magnitude,
 two's complement, or one's complement, and whether the extraordinary value
-is a trap representation or an ordinary value (C99 6.2.6.2).}
+is a trap representation or an ordinary value (C99 and C11 6.2.6.2).}
 
 GCC supports only two's complement integer types, and all bit patterns
 are ordinary values.
 
 @item
 @cite{The rank of any extended integer type relative to another extended
-integer type with the same precision (C99 6.3.1.1).}
+integer type with the same precision (C99 and C11 6.3.1.1).}
 
 GCC does not support any extended integer types.
 @c If it did, there would only be one of each precision and signedness.
@@ -227,66 +252,68 @@
 @item
 @cite{The result of, or the signal raised by, converting an integer to a
 signed integer type when the value cannot be represented in an object of
-that type (C90 6.2.1.2, C99 6.3.1.3).}
+that type (C90 6.2.1.2, C99 and C11 6.3.1.3).}
 
 For conversion to a type of width @math{N}, the value is reduced
 modulo @math{2^N} to be within range of the type; no signal is raised.
 
 @item
 @cite{The results of some bitwise operations on signed integers (C90
-6.3, C99 6.5).}
+6.3, C99 and C11 6.5).}
 
 Bitwise operators act on the representation of the value including
 both the sign and value bits, where the sign bit is considered
 immediately above the highest-value value bit.  Signed @samp{>>} acts
 on negative numbers by sign extension.
 
-GCC does not use the latitude given in C99 only to treat certain
-aspects of signed @samp{<<} as undefined, but this is subject to
-change.
+As an extension to the C language, GCC does not use the latitude given in
+C99 and C11 only to treat certain aspects of signed @samp{<<} as undefined.
+However, @option{-fsanitize=shift} (and @option{-fsanitize=undefined}) will
+diagnose such cases.  They are also diagnosed where constant
+expressions are required.
 
 @item
 @cite{The sign of the remainder on integer division (C90 6.3.5).}
 
-GCC always follows the C99 requirement that the result of division is
+GCC always follows the C99 and C11 requirement that the result of division is
 truncated towards zero.
 
 @end itemize
 
 @node Floating point implementation
-@section Floating point
+@section Floating Point
 
 @itemize @bullet
 @item
 @cite{The accuracy of the floating-point operations and of the library
 functions in @code{<math.h>} and @code{<complex.h>} that return floating-point
-results (C90 and C99 5.2.4.2.2).}
+results (C90, C99 and C11 5.2.4.2.2).}
 
 The accuracy is unknown.
 
 @item
 @cite{The rounding behaviors characterized by non-standard values
 of @code{FLT_ROUNDS} @gol
-(C90 and C99 5.2.4.2.2).}
+(C90, C99 and C11 5.2.4.2.2).}
 
 GCC does not use such values.
 
 @item
 @cite{The evaluation methods characterized by non-standard negative
-values of @code{FLT_EVAL_METHOD} (C99 5.2.4.2.2).}
+values of @code{FLT_EVAL_METHOD} (C99 and C11 5.2.4.2.2).}
 
 GCC does not use such values.
 
 @item
 @cite{The direction of rounding when an integer is converted to a
 floating-point number that cannot exactly represent the original
-value (C90 6.2.1.3, C99 6.3.1.4).}
+value (C90 6.2.1.3, C99 and C11 6.3.1.4).}
 
 C99 Annex F is followed.
 
 @item
 @cite{The direction of rounding when a floating-point number is
-converted to a narrower floating-point number (C90 6.2.1.4, C99
+converted to a narrower floating-point number (C90 6.2.1.4, C99 and C11
 6.3.1.5).}
 
 C99 Annex F is followed.
@@ -294,38 +321,42 @@
 @item
 @cite{How the nearest representable value or the larger or smaller
 representable value immediately adjacent to the nearest representable
-value is chosen for certain floating constants (C90 6.1.3.1, C99
+value is chosen for certain floating constants (C90 6.1.3.1, C99 and C11
 6.4.4.2).}
 
 C99 Annex F is followed.
 
 @item
 @cite{Whether and how floating expressions are contracted when not
-disallowed by the @code{FP_CONTRACT} pragma (C99 6.5).}
+disallowed by the @code{FP_CONTRACT} pragma (C99 and C11 6.5).}
 
-Expressions are currently only contracted if
+Expressions are currently only contracted if @option{-ffp-contract=fast},
 @option{-funsafe-math-optimizations} or @option{-ffast-math} are used.
 This is subject to change.
 
 @item
-@cite{The default state for the @code{FENV_ACCESS} pragma (C99 7.6.1).}
+@cite{The default state for the @code{FENV_ACCESS} pragma (C99 and C11
+7.6.1).}
 
 This pragma is not implemented, but the default is to ``off'' unless
 @option{-frounding-math} is used in which case it is ``on''.
 
 @item
 @cite{Additional floating-point exceptions, rounding modes, environments,
-and classifications, and their macro names (C99 7.6, C99 7.12).}
+and classifications, and their macro names (C99 and C11 7.6, C99 and
+C11 7.12).}
 
 This is dependent on the implementation of the C library, and is not
 defined by GCC itself.
 
 @item
-@cite{The default state for the @code{FP_CONTRACT} pragma (C99 7.12.2).}
+@cite{The default state for the @code{FP_CONTRACT} pragma (C99 and C11
+7.12.2).}
 
 This pragma is not implemented.  Expressions are currently only
-contracted if @option{-funsafe-math-optimizations} or
-@option{-ffast-math} are used.  This is subject to change.
+contracted if @option{-ffp-contract=fast},
+@option{-funsafe-math-optimizations} or @option{-ffast-math} are used.
+This is subject to change.
 
 @item
 @cite{Whether the ``inexact'' floating-point exception can be raised
@@ -346,12 +377,12 @@
 @end itemize
 
 @node Arrays and pointers implementation
-@section Arrays and pointers
+@section Arrays and Pointers
 
 @itemize @bullet
 @item
 @cite{The result of converting a pointer to an integer or
-vice versa (C90 6.3.4, C99 6.3.2.3).}
+vice versa (C90 6.3.4, C99 and C11 6.3.2.3).}
 
 A cast from pointer to integer discards most-significant bits if the
 pointer representation is larger than the integer type,
@@ -374,11 +405,11 @@
 pointer must reference the same object as the original pointer, otherwise
 the behavior is undefined.  That is, one may not use integer arithmetic to
 avoid the undefined behavior of pointer arithmetic as proscribed in
-C99 6.5.6/8.
+C99 and C11 6.5.6/8.
 
 @item
 @cite{The size of the result of subtracting two pointers to elements
-of the same array (C90 6.3.6, C99 6.5.6).}
+of the same array (C90 6.3.6, C99 and C11 6.5.6).}
 
 The value is as specified in the standard and the type is determined
 by the ABI@.
@@ -391,14 +422,14 @@
 @itemize @bullet
 @item
 @cite{The extent to which suggestions made by using the @code{register}
-storage-class specifier are effective (C90 6.5.1, C99 6.7.1).}
+storage-class specifier are effective (C90 6.5.1, C99 and C11 6.7.1).}
 
 The @code{register} specifier affects code generation only in these ways:
 
 @itemize @bullet
 @item
 When used as part of the register variable extension, see
-@ref{Explicit Reg Vars}.
+@ref{Explicit Register Variables}.
 
 @item
 When @option{-O0} is in use, the compiler allocates distinct stack
@@ -416,7 +447,7 @@
 
 @item
 @cite{The extent to which suggestions made by using the inline function
-specifier are effective (C99 6.7.4).}
+specifier are effective (C99 and C11 6.7.4).}
 
 GCC will not inline any functions if the @option{-fno-inline} option is
 used or if @option{-O0} is used.  Otherwise, GCC may still be unable to
@@ -426,7 +457,7 @@
 @end itemize
 
 @node Structures unions enumerations and bit-fields implementation
-@section Structures, unions, enumerations, and bit-fields
+@section Structures, Unions, Enumerations, and Bit-Fields
 
 @itemize @bullet
 @item
@@ -440,7 +471,7 @@
 @item
 @cite{Whether a ``plain'' @code{int} bit-field is treated as a
 @code{signed int} bit-field or as an @code{unsigned int} bit-field
-(C90 6.5.2, C90 6.5.2.1, C99 6.7.2, C99 6.7.2.1).}
+(C90 6.5.2, C90 6.5.2.1, C99 and C11 6.7.2, C99 and C11 6.7.2.1).}
 
 @opindex funsigned-bitfields
 By default it is treated as @code{signed int} but this may be changed
@@ -448,33 +479,37 @@
 
 @item
 @cite{Allowable bit-field types other than @code{_Bool}, @code{signed int},
-and @code{unsigned int} (C99 6.7.2.1).}
+and @code{unsigned int} (C99 and C11 6.7.2.1).}
+
+Other integer types, such as @code{long int}, and enumerated types are
+permitted even in strictly conforming mode.
 
-No other types are permitted in strictly conforming mode.
-@c Would it be better to restrict the pedwarn for other types to C90
-@c mode and document the other types for C99 mode?
+@item
+@cite{Whether atomic types are permitted for bit-fields (C11 6.7.2.1).}
+
+Atomic types are not permitted for bit-fields.
 
 @item
 @cite{Whether a bit-field can straddle a storage-unit boundary (C90
-6.5.2.1, C99 6.7.2.1).}
+6.5.2.1, C99 and C11 6.7.2.1).}
 
 Determined by ABI@.
 
 @item
 @cite{The order of allocation of bit-fields within a unit (C90
-6.5.2.1, C99 6.7.2.1).}
+6.5.2.1, C99 and C11 6.7.2.1).}
 
 Determined by ABI@.
 
 @item
 @cite{The alignment of non-bit-field members of structures (C90
-6.5.2.1, C99 6.7.2.1).}
+6.5.2.1, C99 and C11 6.7.2.1).}
 
 Determined by ABI@.
 
 @item
 @cite{The integer type compatible with each enumerated type (C90
-6.5.2.2, C99 6.7.2.2).}
+6.5.2.2, C99 and C11 6.7.2.2).}
 
 @opindex fshort-enums
 Normally, the type is @code{unsigned int} if there are no negative
@@ -502,7 +537,7 @@
 @itemize @bullet
 @item
 @cite{What constitutes an access to an object that has volatile-qualified
-type (C90 6.5.3, C99 6.7.3).}
+type (C90 6.5.3, C99 and C11 6.7.3).}
 
 Such an object is normally accessed by pointers and used for accessing
 hardware.  In most expressions, it is intuitively obvious what is a read
@@ -568,7 +603,7 @@
 @end itemize
 
 @node Preprocessing directives implementation
-@section Preprocessing directives
+@section Preprocessing Directives
 
 @xref{Implementation-defined behavior, , Implementation-defined
 behavior, cpp, The C Preprocessor}, for details of these aspects of
@@ -576,45 +611,49 @@
 
 @itemize @bullet
 @item
+@cite{The locations within @code{#pragma} directives where header name
+preprocessing tokens are recognized (C11 6.4, C11 6.4.7).}
+
+@item
 @cite{How sequences in both forms of header names are mapped to headers
-or external source file names (C90 6.1.7, C99 6.4.7).}
+or external source file names (C90 6.1.7, C99 and C11 6.4.7).}
 
 @item
 @cite{Whether the value of a character constant in a constant expression
 that controls conditional inclusion matches the value of the same character
-constant in the execution character set (C90 6.8.1, C99 6.10.1).}
+constant in the execution character set (C90 6.8.1, C99 and C11 6.10.1).}
 
 @item
 @cite{Whether the value of a single-character character constant in a
 constant expression that controls conditional inclusion may have a
-negative value (C90 6.8.1, C99 6.10.1).}
+negative value (C90 6.8.1, C99 and C11 6.10.1).}
 
 @item
 @cite{The places that are searched for an included @samp{<>} delimited
 header, and how the places are specified or the header is
-identified (C90 6.8.2, C99 6.10.2).}
+identified (C90 6.8.2, C99 and C11 6.10.2).}
 
 @item
 @cite{How the named source file is searched for in an included @samp{""}
-delimited header (C90 6.8.2, C99 6.10.2).}
+delimited header (C90 6.8.2, C99 and C11 6.10.2).}
 
 @item
 @cite{The method by which preprocessing tokens (possibly resulting from
 macro expansion) in a @code{#include} directive are combined into a header
-name (C90 6.8.2, C99 6.10.2).}
+name (C90 6.8.2, C99 and C11 6.10.2).}
 
 @item
 @cite{The nesting limit for @code{#include} processing (C90 6.8.2, C99
-6.10.2).}
+and C11 6.10.2).}
 
 @item
 @cite{Whether the @samp{#} operator inserts a @samp{\} character before
 the @samp{\} character that begins a universal character name in a
-character constant or string literal (C99 6.10.3.2).}
+character constant or string literal (C99 and C11 6.10.3.2).}
 
 @item
 @cite{The behavior on each recognized non-@code{STDC #pragma}
-directive (C90 6.8.6, C99 6.10.6).}
+directive (C90 6.8.6, C99 and C11 6.10.6).}
 
 @xref{Pragmas, , Pragmas, cpp, The C Preprocessor}, for details of
 pragmas accepted by GCC on all targets.  @xref{Pragmas, , Pragmas
@@ -623,12 +662,12 @@
 @item
 @cite{The definitions for @code{__DATE__} and @code{__TIME__} when
 respectively, the date and time of translation are not available (C90
-6.8.8, C99 6.10.8).}
+6.8.8, C99 6.10.8, C11 6.10.8.1).}
 
 @end itemize
 
 @node Library functions implementation
-@section Library functions
+@section Library Functions
 
 The behavior of most of these points are dependent on the implementation
 of the C library, and are not defined by GCC itself.
@@ -636,7 +675,7 @@
 @itemize @bullet
 @item
 @cite{The null pointer constant to which the macro @code{NULL} expands
-(C90 7.1.6, C99 7.17).}
+(C90 7.1.6, C99 7.17, C11 7.19).}
 
 In @code{<stddef.h>}, @code{NULL} expands to @code{((void *)0)}.  GCC
 does not provide the other headers which define @code{NULL} and some
@@ -651,26 +690,51 @@
 @item
 @cite{The values or expressions assigned to the macros specified in the
 headers @code{<float.h>}, @code{<limits.h>}, and @code{<stdint.h>}
-(C90 and C99 5.2.4.2, C99 7.18.2, C99 7.18.3).}
+(C90, C99 and C11 5.2.4.2, C99 7.18.2, C99 7.18.3, C11 7.20.2, C11 7.20.3).}
 
 Determined by ABI@.
 
 @item
+@cite{The result of attempting to indirectly access an object with
+automatic or thread storage duration from a thread other than the one
+with which it is associated (C11 6.2.4).}
+
+Such accesses are supported, subject to the same requirements for
+synchronization for concurrent accesses as for concurrent accesses to
+any object.
+
+@item
 @cite{The number, order, and encoding of bytes in any object
-(when not explicitly specified in this International Standard) (C99 6.2.6.1).}
+(when not explicitly specified in this International Standard) (C99
+and C11 6.2.6.1).}
 
 Determined by ABI@.
 
 @item
-@cite{The value of the result of the @code{sizeof} operator (C90
-6.3.3.4, C99 6.5.3.4).}
+@cite{Whether any extended alignments are supported and the contexts
+in which they are supported (C11 6.2.8).}
+
+Extended alignments up to @math{2^{28}} (bytes) are supported for
+objects of automatic storage duration.  Alignments supported for
+objects of static and thread storage duration are determined by the
+ABI.
+
+@item
+@cite{Valid alignment values other than those returned by an _Alignof
+expression for fundamental types, if any (C11 6.2.8).}
+
+Valid alignments are powers of 2 up to and including @math{2^{28}}.
+
+@item
+@cite{The value of the result of the @code{sizeof} and @code{_Alignof}
+operators (C90 6.3.3.4, C99 and C11 6.5.3.4).}
 
 Determined by ABI@.
 
 @end itemize
 
 @node Locale-specific behavior implementation
-@section Locale-specific behavior
+@section Locale-Specific Behavior
 
 The behavior of these points are dependent on the implementation
 of the C library, and are not defined by GCC itself.