From 8b401988f8558104b56c0ee36a4e75b1230ad371 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 5 May 2011 22:43:18 -0700 Subject: [PATCH] assert-h: new module, which supports C1X-style static_assert * lib/assert.in.h, m4/assert_h.m4, modules/assert-h: New files. * lib/verify.h: Revamp so that this can be copied into assert.h, while retaining the ability to use it standalone as before. Rename private identifiers so as not to encroach on the standard C namespace, since this is now used by assert.h. (_GL_VERIFY_TYPE): New macro, factoring out differing parts of the old verify_true. (_GL_VERIFY_TRUE): New macro, with much of the contents of the old verify_true. Use _GL_VERIFY_TYPE. (_GL_VERIFY): New macro, with much of the contents of the old verify. (static_assert): New macro, if _GL_STATIC_ASSERT_H is defined and static_assert is not; _GL_STATIC_ASSERT_H is defined when this file is copied into the replacement assert.h. (_Static_assert): New macro, if _GL_STATIC_ASSERT_H is defined and _Static_assert is not built in. (verify_true, verify): Define only if _GL_STATIC_ASSERT_H is not defined, and use the new macros mentioned above. * doc/posix-headers/assert.texi: Document this. --- ChangeLog | 22 +++++++ doc/posix-headers/assert.texi | 21 ++++++- lib/assert.in.h | 28 +++++++++ lib/verify.h | 130 +++++++++++++++++++++++++----------------- m4/assert_h.m4 | 29 ++++++++++ modules/assert-h | 47 +++++++++++++++ 6 files changed, 225 insertions(+), 52 deletions(-) create mode 100644 lib/assert.in.h create mode 100644 m4/assert_h.m4 create mode 100644 modules/assert-h diff --git a/ChangeLog b/ChangeLog index 3c60a4e8e..b57e17bea 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,25 @@ +2011-05-05 Paul Eggert + + assert-h: new module, which supports C1X-style static_assert + * lib/assert.in.h, m4/assert_h.m4, modules/assert-h: New files. + * lib/verify.h: Revamp so that this can be copied into assert.h, + while retaining the ability to use it standalone as before. + Rename private identifiers so as not to encroach on the + standard C namespace, since this is now used by assert.h. + (_GL_VERIFY_TYPE): New macro, factoring out differing parts of + the old verify_true. + (_GL_VERIFY_TRUE): New macro, with much of the contents of + the old verify_true. Use _GL_VERIFY_TYPE. + (_GL_VERIFY): New macro, with much of the contents of the old verify. + (static_assert): New macro, if _GL_STATIC_ASSERT_H + is defined and static_assert is not; _GL_STATIC_ASSERT_H is + defined when this file is copied into the replacement assert.h. + (_Static_assert): New macro, if _GL_STATIC_ASSERT_H is defined + and _Static_assert is not built in. + (verify_true, verify): Define only if _GL_STATIC_ASSERT_H is not + defined, and use the new macros mentioned above. + * doc/posix-headers/assert.texi: Document this. + 2011-05-05 Bruno Haible fclose, fflush: Respect rules for use of AC_LIBOBJ. diff --git a/doc/posix-headers/assert.texi b/doc/posix-headers/assert.texi index 02a1c3b54..aa78ee7bc 100644 --- a/doc/posix-headers/assert.texi +++ b/doc/posix-headers/assert.texi @@ -3,12 +3,31 @@ POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/basedefs/assert.h.html} -Gnulib module: --- +Gnulib module: assert-h + +See also the Gnulib module @code{assert}. Portability problems fixed by Gnulib: @itemize +@item +The draft C1X and C++0X @code{static_assert}, and the draft C1X +@code{_Static_assert}, are not supported by many platforms. +For example, GCC versions before 4.6.0 do not support @code{_Static_assert}, +and G++ versions through at least 4.6.0 do not support @code{static_assert}. @end itemize Portability problems not fixed by Gnulib: @itemize +@item +Draft C1X @code{_Static_assert} and draft C++0X @code{static_assert} +are keywords that can be used without including @code{}. +The Gnulib substitutes are macros that require including @code{}. +@item +The draft C1X @code{static_assert} and @code{_Static_assert} can also +be used within a @code{struct} or @code{union} specifier, in place of +an ordinary declaration of a member of the struct or union. The +Gnulib substitute can be used only as an ordinary declaration. +@item +In C99, @code{assert} can be applied to any scalar expression. +In C89, the argument to @code{assert} is of type @code{int}. @end itemize diff --git a/lib/assert.in.h b/lib/assert.in.h new file mode 100644 index 000000000..1857cebbb --- /dev/null +++ b/lib/assert.in.h @@ -0,0 +1,28 @@ +/* Substitute for and wrapper around + Copyright (C) 2011 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* Do not guard the include, since is supposed to define + the assert macro each time it is included. */ + +#if __GNUC__ >= 3 +@PRAGMA_SYSTEM_HEADER@ +#endif +@PRAGMA_COLUMNS@ + +#@INCLUDE_NEXT@ @NEXT_ASSERT_H@ + +/* The definition of static_assert is copied here. */ diff --git a/lib/verify.h b/lib/verify.h index 6bca43f6a..e5065ffa0 100644 --- a/lib/verify.h +++ b/lib/verify.h @@ -17,42 +17,37 @@ /* 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 HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the + +/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the C1X draft N1548 section 6.7.10. 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 HAVE_STATIC_ASSERT to 1 if static_assert works as per the - C1X draft N1548 section 7.2 or the C++0X draft N3242 section 7.(4). + Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per the + C++0X draft N3242 section 7.(4). This will likely be supported by future GCC versions, in C++ mode. - For now, use this only with GCC. Eventually whether _Static_assert - and static_assert works should be determined by 'configure'. */ + 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__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus -# define HAVE__STATIC_ASSERT 1 +# 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 HAVE_STATIC_ASSERT 1 +# define _GL_HAVE_STATIC_ASSERT 1 # 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, - verify_true (R) works by packaging a _Static_assert inside a struct + _GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct that is an operand of sizeof. The code below uses several ideas for C++ compilers, and for C @@ -64,7 +59,9 @@ 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. @@ -78,7 +75,7 @@ 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, @@ -116,11 +113,11 @@ 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 @@ -159,44 +156,75 @@ possible. */ # define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER) -/* Verify requirement R at compile-time, as an integer constant expression. - Return 1. */ +/* 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 template - struct verify_type__ { unsigned int verify_error_if_negative_size__: w; }; -# define verify_true(R) \ - (!!sizeof (verify_type__<(R) ? 1 : -1>)) -# elif HAVE__STATIC_ASSERT -# define verify_true(R) \ - (!!sizeof \ - (struct { \ - _Static_assert (R, "verify_true (" #R ")"); \ - int verify_dummy__; \ - })) -# elif HAVE_STATIC_ASSERT -# define verify_true(R) \ - (!!sizeof \ - (struct { \ - static_assert (R, "verify_true (" #R ")"); \ - int verify_dummy__; \ - })) + struct _gl_verify_type { + unsigned int _gl_verify_error_if_negative: w; + }; +# 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 verify_true(R) \ - (!!sizeof \ - (struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; })) +# 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 ';'. */ + trailing ';'. If R is false, fail at compile-time, preferably + with a diagnostic that includes the string-literal DIAGNOSTIC. + + Unfortunately, unlike C1X, 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 -# if HAVE__STATIC_ASSERT -# define verify(R) _Static_assert (R, "verify (" #R ")") -# elif HAVE_STATIC_ASSERT -# define verify(R) static_assert (R, "verify (" #R ")") +/* _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 /* Draft C1X requires this #define. */ +# endif # else -# define verify(R) \ - extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)] + +/* 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. */ + +# define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")") + +/* Verify requirement R at compile-time, as a declaration without a + trailing ';'. */ + +# define verify(R) _GL_VERIFY (R, "verify (" #R ")") + # endif #endif diff --git a/m4/assert_h.m4 b/m4/assert_h.m4 new file mode 100644 index 000000000..30ca24894 --- /dev/null +++ b/m4/assert_h.m4 @@ -0,0 +1,29 @@ +# assert-h.m4 +dnl Copyright (C) 2011 Free Software Foundation, Inc. +dnl This file is free software; the Free Software Foundation +dnl gives unlimited permission to copy and/or distribute it, +dnl with or without modifications, as long as this notice is preserved. + +dnl From Paul Eggert. + +AC_DEFUN([gl_ASSERT_H], +[ + ASSERT_H= + AC_CACHE_CHECK([for static_assert], [gl_cv_static_assert], + [AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM( + [[#include + static_assert (2 + 2 == 4, "arithmetic doesn't work"); + ]], + [[ + static_assert (sizeof (char) == 1, "sizeof doesn't work"); + ]])], + [gl_cv_static_assert=yes], + [gl_cv_static_assert=no])]) + if test $gl_cv_static_assert = no; then + ASSERT_H=assert.h + gl_NEXT_HEADERS([assert.h]) + fi + AC_SUBST([ASSERT_H]) + AM_CONDITIONAL([GL_GENERATE_ASSERT_H], [test -n "$ASSERT_H"]) +]) diff --git a/modules/assert-h b/modules/assert-h new file mode 100644 index 000000000..50bd9f83e --- /dev/null +++ b/modules/assert-h @@ -0,0 +1,47 @@ +Description: +An that conforms to C1X. + +Files: +lib/assert.in.h +lib/verify.h +m4/assert_h.m4 + +Depends-on: +include_next + +configure.ac: +gl_ASSERT_H + +Makefile.am: +BUILT_SOURCES += $(ASSERT_H) + +# We need the following in order to create when the system +# doesn't have one that works with the given compiler. +if GL_GENERATE_ASSERT_H +assert.h: assert.in.h verify.h $(top_builddir)/config.status + $(AM_V_GEN)rm -f $@-t $@ && \ + { echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */' && \ + sed -e 's|@''INCLUDE_NEXT''@|$(INCLUDE_NEXT)|g' \ + -e 's|@''PRAGMA_SYSTEM_HEADER''@|@PRAGMA_SYSTEM_HEADER@|g' \ + -e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \ + -e 's|@''NEXT_ASSERT_H''@|$(NEXT_ASSERT_H)|g' \ + < $(srcdir)/assert.in.h && \ + sed -e 's|_gl_verify|_gl_static_assert|g' \ + -e 's|_GL_VERIFY|_GL_STATIC_ASSERT|g' \ + < $(srcdir)/verify.h; \ + } > $@-t && \ + mv $@-t $@ +else +assert.h: $(top_builddir)/config.status + rm -f $@ +endif +MOSTLYCLEANFILES += assert.h assert.h-t + +Include: + + +License: +LGPLv2+ + +Maintainer: +Paul Eggert -- 2.11.0