From 9886b7a922fd90cc86b19106293250da652256aa Mon Sep 17 00:00:00 2001 From: Zack Weinberg Date: Sat, 28 Nov 2020 11:08:28 -0500 Subject: [PATCH] Disentangle HAVE__BOOL from ac_cv_header_stdbool_h. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit AC_CHECK_HEADER_STDBOOL is documented to make two checks: whether the C99 header is available and fulfills its specification (i.e. including it makes the type ‘bool’ and the constants ‘true’ and ‘false’ available), and, independently, whether the type ‘_Bool’ is available. In C++, the type ‘_Bool’ is usually _not_ available, but is still supposed to be include-able and the type ‘bool’ and the constants ‘true’ and ‘false’ are still supposed to be available (unconditionally). However, the test for fulfilling its specification freely used _Bool, and would therefore fail spuriously. Correct this by checking for _Bool first, and then refactoring the test program for so that it does all its tests using bool, then repeats them with _Bool only when available. * lib/autoconf/headers.m4 (AC_CHECK_HEADER_STDBOOL): Do the test for _Bool before the test for stdbool.h. Test semantics of bool unconditionally; test _Bool only when HAVE__BOOL is defined. --- lib/autoconf/headers.m4 | 138 ++++++++++++++++++++++++++-------------- 1 file changed, 91 insertions(+), 47 deletions(-) diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4 index 3b97a185..17a5abac 100644 --- a/lib/autoconf/headers.m4 +++ b/lib/autoconf/headers.m4 @@ -574,70 +574,114 @@ AN_IDENTIFIER([bool], [AC_CHECK_HEADER_STDBOOL]) AN_IDENTIFIER([true], [AC_CHECK_HEADER_STDBOOL]) AN_IDENTIFIER([false],[AC_CHECK_HEADER_STDBOOL]) AC_DEFUN([AC_CHECK_HEADER_STDBOOL], - [AC_CACHE_CHECK([for stdbool.h that conforms to C99], + [AC_CHECK_TYPES([_Bool]) + AC_CACHE_CHECK([for stdbool.h that conforms to C99], [ac_cv_header_stdbool_h], [AC_COMPILE_IFELSE( [AC_LANG_PROGRAM( - [[ - #include - - #if __cplusplus < 201103 - #ifndef bool - "error: bool is not defined" - #endif - #ifndef false - "error: false is not defined" - #endif - #if false - "error: false is not 0" - #endif - #ifndef true - "error: true is not defined" - #endif - #if true != 1 - "error: true is not 1" - #endif - #endif + [[#include #ifndef __bool_true_false_are_defined - "error: __bool_true_false_are_defined is not defined" + #error "__bool_true_false_are_defined is not defined" #endif + char a[__bool_true_false_are_defined == 1 ? 1 : -1]; - struct s { _Bool s: 1; _Bool t; } s; + /* Regardless of whether this is C++ or "_Bool" is a + valid type name, "true" and "false" should be usable + in #if expressions and integer constant expressions, + and "bool" should be a valid type name. */ + + #if !true + #error "'true' is not true" + #endif + #if true != 1 + #error "'true' is not equal to 1" + #endif + char b[true == 1 ? 1 : -1]; + char c[true]; + + #if false + #error "'false' is not false" + #endif + #if false != 0 + #error "'false' is not equal to 0" + #endif + char d[false == 0 ? 1 : -1]; + + enum { e = false, f = true, g = false * true, h = true * 256 }; + + char i[(bool) 0.5 == true ? 1 : -1]; + char j[(bool) 0.0 == false ? 1 : -1]; + char k[sizeof (bool) > 0 ? 1 : -1]; + + struct sb { bool s: 1; bool t; } s; + char l[sizeof s.t > 0 ? 1 : -1]; - char a[true == 1 ? 1 : -1]; - char b[false == 0 ? 1 : -1]; - char c[__bool_true_false_are_defined == 1 ? 1 : -1]; - char d[(bool) 0.5 == true ? 1 : -1]; - /* See body of main program for 'e'. */ - char f[(_Bool) 0.0 == false ? 1 : -1]; - char g[true]; - char h[sizeof (_Bool)]; - char i[sizeof s.t]; - enum { j = false, k = true, l = false * true, m = true * 256 }; /* The following fails for HP aC++/ANSI C B3910B A.05.55 [Dec 04 2003]. */ - _Bool n[m]; - char o[sizeof n == m * sizeof n[0] ? 1 : -1]; - char p[-1 - (_Bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1]; + bool m[h]; + char n[sizeof m == h * sizeof m[0] ? 1 : -1]; + char o[-1 - (bool) 0 < 0 ? 1 : -1]; /* Catch a bug in an HP-UX C compiler. See - https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html - https://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html + https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html + https://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html */ - _Bool q = true; - _Bool *pq = &q; + bool p = true; + bool *pp = &p; + + /* C 1999 specifies that bool, true, and false are to be + macros, but C++ 2011 and later overrule this. */ + #if __cplusplus < 201103 + #ifndef bool + #error "bool is not defined" + #endif + #ifndef false + #error "false is not defined" + #endif + #ifndef true + #error "true is not defined" + #endif + #endif + + /* If _Bool is available, repeat with it all the tests + above that used bool. */ + #ifdef HAVE__BOOL + struct sB { _Bool s: 1; _Bool t; } t; + + char q[(_Bool) 0.5 == true ? 1 : -1]; + char r[(_Bool) 0.0 == false ? 1 : -1]; + char u[sizeof (_Bool) > 0 ? 1 : -1]; + char v[sizeof t.t > 0 ? 1 : -1]; + + _Bool w[h]; + char x[sizeof m == h * sizeof m[0] ? 1 : -1]; + char y[-1 - (_Bool) 0 < 0 ? 1 : -1]; + _Bool z = true; + _Bool *pz = &p; + #endif ]], [[ - bool e = &s; - *pq |= q; - *pq |= ! q; - /* Refer to every declared value, to avoid compiler optimizations. */ - return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !!j + !k + !!l - + !m + !n + !o + !p + !q + !pq); + bool ps = &s; + *pp |= p; + *pp |= ! p; + + #ifdef HAVE__BOOL + _Bool pt = &t; + *pz |= z; + *pz |= ! z; + #endif + + /* Refer to every declared value, so they cannot be + discarded as unused. */ + return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !j + !k + + !l + !m + !n + !o + !p + !pp + !ps + #ifdef HAVE__BOOL + + !q + !r + !u + !v + !w + !x + !y + !z + !pt + #endif + ); ]])], [ac_cv_header_stdbool_h=yes], [ac_cv_header_stdbool_h=no])]) - AC_CHECK_TYPES([_Bool]) ])# AC_CHECK_HEADER_STDBOOL