Imported Upstream version 0.9.6upstream/0.9.6

1 files changed, 178 insertions, 39 deletions

diff --git a/lib/verify.h b/lib/verify.h
index 7773c794..db52900e 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -1,6 +1,6 @@
 /* Compile-time assert-like macros.
 
-   Copyright (C) 2005-2006, 2009-2010 Free Software Foundation, Inc.
+   Copyright (C) 2005-2006, 2009-2015 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
@@ -17,21 +17,49 @@
 
 /* Written by Paul Eggert, Bruno Haible, and Jim Meyering.  */
 
-#ifndef VERIFY_H
-# define VERIFY_H 1
+#ifndef _GL_VERIFY_H
+#define _GL_VERIFY_H
+
+
+/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per C11.
+   This is supported by GCC 4.6.0 and later, in C mode, and its use
+   here generates easier-to-read diagnostics when verify (R) fails.
+
+   Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per C++11.
+   This will likely be supported by future GCC versions, in C++ mode.
+
+   Use this only with GCC.  If we were willing to slow 'configure'
+   down we could also use it with other compilers, but since this
+   affects only the quality of diagnostics, why bother?  */
+#if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \
+     && (201112L <= __STDC_VERSION__  || !defined __STRICT_ANSI__) \
+     && !defined __cplusplus)
+# define _GL_HAVE__STATIC_ASSERT 1
+#endif
+/* The condition (99 < __GNUC__) is temporary, until we know about the
+   first G++ release that supports static_assert.  */
+#if (99 < __GNUC__) && defined __cplusplus
+# define _GL_HAVE_STATIC_ASSERT 1
+#endif
+
+/* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
+   system headers, defines a conflicting _Static_assert that is no
+   better than ours; override it.  */
+#ifndef _GL_HAVE_STATIC_ASSERT
+# include <stddef.h>
+# undef _Static_assert
+#endif
 
 /* Each of these macros verifies that its argument R is nonzero.  To
    be portable, R should be an integer constant expression.  Unlike
    assert (R), there is no run-time overhead.
 
-   There are two macros, since no single macro can be used in all
-   contexts in C.  verify_true (R) is for scalar contexts, including
-   integer constant expression contexts.  verify (R) is for declaration
-   contexts, e.g., the top level.
-
-   Symbols ending in "__" are private to this header.
+   If _Static_assert works, verify (R) uses it directly.  Similarly,
+   _GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct
+   that is an operand of sizeof.
 
-   The code below uses several ideas.
+   The code below uses several ideas for C++ compilers, and for C
+   compilers that do not support _Static_assert:
 
    * The first step is ((R) ? 1 : -1).  Given an expression R, of
      integral or boolean or floating-point type, this yields an
@@ -39,7 +67,9 @@
      constant and nonnegative.
 
    * Next this expression W is wrapped in a type
-     struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }.
+     struct _gl_verify_type {
+       unsigned int _gl_verify_error_if_negative: W;
+     }.
      If W is negative, this yields a compile-time error.  No compiler can
      deal with a bit-field of negative size.
 
@@ -53,7 +83,7 @@
 
        void function (int n) { verify (n < 0); }
 
-   * For the verify macro, the struct verify_type__ will need to
+   * For the verify macro, the struct _gl_verify_type will need to
      somehow be embedded into a declaration.  To be portable, this
      declaration must declare an object, a constant, a function, or a
      typedef name.  If the declared entity uses the type directly,
@@ -69,13 +99,14 @@
      if the entity names are not disambiguated.  A workaround is to
      attach the current line number to the entity name:
 
-       #define GL_CONCAT0(x, y) x##y
-       #define GL_CONCAT(x, y) GL_CONCAT0 (x, y)
-       extern struct {...} * GL_CONCAT(dummy,__LINE__);
+       #define _GL_CONCAT0(x, y) x##y
+       #define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
+       extern struct {...} * _GL_CONCAT (dummy, __LINE__);
 
      But this has the problem that two invocations of verify from
      within the same macro would collide, since the __LINE__ value
-     would be the same for both invocations.
+     would be the same for both invocations.  (The GCC __COUNTER__
+     macro solves this problem, but is not portable.)
 
      A solution is to use the sizeof operator.  It yields a number,
      getting rid of the identity of the type.  Declarations like
@@ -90,11 +121,11 @@
      Which of the following alternatives can be used?
 
        extern int dummy [sizeof (struct {...})];
-       extern int dummy [sizeof (struct verify_type__ {...})];
+       extern int dummy [sizeof (struct _gl_verify_type {...})];
        extern void dummy (int [sizeof (struct {...})]);
-       extern void dummy (int [sizeof (struct verify_type__ {...})]);
+       extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
        extern int (*dummy (void)) [sizeof (struct {...})];
-       extern int (*dummy (void)) [sizeof (struct verify_type__ {...})];
+       extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
 
      In the second and sixth case, the struct type is exported to the
      outer scope; two such declarations therefore collide.  GCC warns
@@ -103,38 +134,146 @@
 
        extern int (*dummy (void)) [sizeof (struct {...})];
 
-   * This implementation exploits the fact that GCC does not warn about
-     the last declaration mentioned above.  If a future version of GCC
-     introduces a warning for this, the problem could be worked around
-     by using code specialized to GCC, e.g.,:
+   * GCC warns about duplicate declarations of the dummy function if
+     -Wredundant-decls is used.  GCC 4.3 and later have a builtin
+     __COUNTER__ macro that can let us generate unique identifiers for
+     each dummy function, to suppress this warning.
 
-       #if 4 <= __GNUC__
-       # define verify(R) \
-           extern int (* verify_function__ (void)) \
-                      [__builtin_constant_p (R) && (R) ? 1 : -1]
-       #endif
+   * This implementation exploits the fact that older versions of GCC,
+     which do not support _Static_assert, also do not warn about the
+     last declaration mentioned above.
+
+   * GCC warns if -Wnested-externs is enabled and verify() is used
+     within a function body; but inside a function, you can always
+     arrange to use verify_expr() instead.
 
    * In C++, any struct definition inside sizeof is invalid.
      Use a template type to work around the problem.  */
 
+/* Concatenate two preprocessor tokens.  */
+#define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
+#define _GL_CONCAT0(x, y) x##y
+
+/* _GL_COUNTER is an integer, preferably one that changes each time we
+   use it.  Use __COUNTER__ if it works, falling back on __LINE__
+   otherwise.  __LINE__ isn't perfect, but it's better than a
+   constant.  */
+#if defined __COUNTER__ && __COUNTER__ != __COUNTER__
+# define _GL_COUNTER __COUNTER__
+#else
+# define _GL_COUNTER __LINE__
+#endif
 
-/* Verify requirement R at compile-time, as an integer constant expression.
-   Return 1.  */
+/* Generate a symbol with the given prefix, making it unique if
+   possible.  */
+#define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
 
-# ifdef __cplusplus
+/* Verify requirement R at compile-time, as an integer constant expression
+   that returns 1.  If R is false, fail at compile-time, preferably
+   with a diagnostic that includes the string-literal DIAGNOSTIC.  */
+
+#define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
+   (!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
+
+#ifdef __cplusplus
+# if !GNULIB_defined_struct__gl_verify_type
 template <int w>
-  struct verify_type__ { unsigned int verify_error_if_negative_size__: w; };
-#  define verify_true(R) \
-     (!!sizeof (verify_type__<(R) ? 1 : -1>))
-# else
-#  define verify_true(R) \
-     (!!sizeof \
-      (struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; }))
+  struct _gl_verify_type {
+    unsigned int _gl_verify_error_if_negative: w;
+  };
+#  define GNULIB_defined_struct__gl_verify_type 1
 # endif
+# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
+    _gl_verify_type<(R) ? 1 : -1>
+#elif defined _GL_HAVE__STATIC_ASSERT
+# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
+    struct {                                   \
+      _Static_assert (R, DIAGNOSTIC);          \
+      int _gl_dummy;                          \
+    }
+#else
+# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
+    struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
+#endif
+
+/* Verify requirement R at compile-time, as a declaration without a
+   trailing ';'.  If R is false, fail at compile-time, preferably
+   with a diagnostic that includes the string-literal DIAGNOSTIC.
+
+   Unfortunately, unlike C11, this implementation must appear as an
+   ordinary declaration, and cannot appear inside struct { ... }.  */
+
+#ifdef _GL_HAVE__STATIC_ASSERT
+# define _GL_VERIFY _Static_assert
+#else
+# define _GL_VERIFY(R, DIAGNOSTIC)				       \
+    extern int (*_GL_GENSYM (_gl_verify_function) (void))	       \
+      [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
+#endif
+
+/* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h.  */
+#ifdef _GL_STATIC_ASSERT_H
+# if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert
+#  define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
+# endif
+# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
+#  define static_assert _Static_assert /* C11 requires this #define.  */
+# endif
+#endif
+
+/* @assert.h omit start@  */
+
+/* Each of these macros verifies that its argument R is nonzero.  To
+   be portable, R should be an integer constant expression.  Unlike
+   assert (R), there is no run-time overhead.
+
+   There are two macros, since no single macro can be used in all
+   contexts in C.  verify_true (R) is for scalar contexts, including
+   integer constant expression contexts.  verify (R) is for declaration
+   contexts, e.g., the top level.  */
+
+/* Verify requirement R at compile-time, as an integer constant expression.
+   Return 1.  This is equivalent to verify_expr (R, 1).
+
+   verify_true is obsolescent; please use verify_expr instead.  */
+
+#define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")
+
+/* Verify requirement R at compile-time.  Return the value of the
+   expression E.  */
+
+#define verify_expr(R, E) \
+   (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E))
 
 /* Verify requirement R at compile-time, as a declaration without a
    trailing ';'.  */
 
-# define verify(R) extern int (* verify_function__ (void)) [verify_true (R)]
+#define verify(R) _GL_VERIFY (R, "verify (" #R ")")
+
+#ifndef __has_builtin
+# define __has_builtin(x) 0
+#endif
+
+/* Assume that R always holds.  This lets the compiler optimize
+   accordingly.  R should not have side-effects; it may or may not be
+   evaluated.  Behavior is undefined if R is false.  */
+
+#if (__has_builtin (__builtin_unreachable) \
+     || 4 < __GNUC__ + (5 <= __GNUC_MINOR__))
+# define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())
+#elif 1200 <= _MSC_VER
+# define assume(R) __assume (R)
+#elif (defined lint \
+       && (__has_builtin (__builtin_trap) \
+           || 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))))
+  /* Doing it this way helps various packages when configured with
+     --enable-gcc-warnings, which compiles with -Dlint.  It's nicer
+     when 'assume' silences warnings even with older GCCs.  */
+# define assume(R) ((R) ? (void) 0 : __builtin_trap ())
+#else
+# define assume(R) ((void) (0 && (R)))
+#endif
+
+/* @assert.h omit end@  */
 
 #endif