From: Paul Eggert Date: Sat, 4 Feb 2023 23:53:40 +0000 (-0800) Subject: Update some commentary for C23 X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=d27d9a43d4d1b3f8a213cb739f4d27793158a050;p=emacs.git Update some commentary for C23 --- diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi index e1a4613875c..deb1021283f 100644 --- a/doc/lispref/internals.texi +++ b/doc/lispref/internals.texi @@ -732,14 +732,15 @@ Emacs session. @section C Dialect @cindex C programming language -The C part of Emacs is portable to C99 or later: C11-specific features such -as @samp{} and @samp{_Noreturn} are not used without a check, +The C part of Emacs is portable to C99 or later: later C features such +as @samp{} and @samp{[[noreturn]]} are not used without a check, typically at configuration time, and the Emacs build procedure -provides a substitute implementation if necessary. Some C11 features, +provides a substitute implementation if necessary. Some later features, such as anonymous structures and unions, are too difficult to emulate, so they are avoided entirely. -At some point in the future the base C dialect will no doubt change to C11. +At some point in the future the base C dialect will no doubt change to +something later than C99. @node Writing Emacs Primitives @section Writing Emacs Primitives @@ -894,15 +895,17 @@ Currently, only the following attributes are recognized: @table @code @item noreturn Declares the C function as one that never returns. This corresponds -to the C11 keyword @code{_Noreturn} and to @w{@code{__attribute__ -((__noreturn__))}} attribute of GCC (@pxref{Function Attributes,,, -gcc, Using the GNU Compiler Collection}). +to C23's @code{[[noreturn]]}, to C11's @code{_Noreturn}, and to GCC's +@w{@code{__attribute__ ((__noreturn__))}} (@pxref{Function +Attributes,,, gcc, Using the GNU Compiler Collection}). (Internally, +Emacs's own C code uses @code{_Noreturn} as it can be defined as a +macro on C platforms that do not support it.) @item const Declares that the function does not examine any values except its arguments, and has no effects except the return value. This -corresponds to @w{@code{__attribute__ ((__const__))}} attribute of -GCC. +corresponds to C23's @code{[[unsequenced]]} and to GCC's +@w{@code{__attribute__ ((__const__))}}. @item noinline This corresponds to @w{@code{__attribute__ ((__noinline__))}} diff --git a/src/floatfns.c b/src/floatfns.c index 1d891ef3ce1..13f0ca3e129 100644 --- a/src/floatfns.c +++ b/src/floatfns.c @@ -27,19 +27,22 @@ along with GNU Emacs. If not, see . */ frexp, ldexp, log, log10 [via (log X 10)], *modf, pow, sin, *sinh, sqrt, tan, *tanh. - C99 and C11 require the following math.h functions in addition to + C99, C11 and C17 require the following math.h functions in addition to the C89 functions. Of these, Emacs currently exports only the starred ones to Lisp, since we haven't found a use for the others. Also, it uses the ones marked "+" internally: acosh, atanh, cbrt, copysign (implemented by signbit), erf, erfc, exp2, expm1, fdim, fma, fmax, fmin, fpclassify, hypot, +ilogb, - isfinite, isgreater, isgreaterequal, isinf, isless, islessequal, + +isfinite, isgreater, isgreaterequal, +isinf, isless, islessequal, islessgreater, *isnan, isnormal, isunordered, lgamma, log1p, *log2 [via (log X 2)], logb (approximately; implemented by frexp), +lrint/llrint, +lround/llround, nan, nearbyint, nextafter, nexttoward, remainder, remquo, *rint, round, scalbln, +scalbn, +signbit, tgamma, *trunc. + C23 requires many more math.h functions. Emacs does not yet export + or use them. + The C standard also requires functions for float and long double that are not listed above. Of these functions, Emacs uses only the following internally: fabsf, powf, sprintf. diff --git a/src/lisp.h b/src/lisp.h index 196615effd8..0bc400ba78f 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -272,7 +272,7 @@ DEFINE_GDB_SYMBOL_END (VALMASK) emacs_align_type union in alloc.c. Although these macros are reasonably portable, they are not - guaranteed on non-GCC platforms, as C11 does not require support + guaranteed on non-GCC platforms, as the C standard does not require support for alignment to GCALIGNMENT and older compilers may ignore alignment requests. For any type T where garbage collection requires alignment, use verify (GCALIGNED (T)) to verify the @@ -2962,9 +2962,10 @@ XFLOAT_DATA (Lisp_Object f) /* Most hosts nowadays use IEEE floating point, so they use IEC 60559 representations, have infinities and NaNs, and do not trap on exceptions. Define IEEE_FLOATING_POINT to 1 if this host is one of the - typical ones. The C11 macro __STDC_IEC_559__ is close to what is + typical ones. The C23 macro __STDC_IEC_60559_BFP__ (or its + obsolescent C11 counterpart __STDC_IEC_559__) is close to what is wanted here, but is not quite right because Emacs does not require - all the features of C11 Annex F (and does not require C11 at all, + all the features of C23 Annex F (and does not require C11 or later, for that matter). */ #define IEEE_FLOATING_POINT (FLT_RADIX == 2 && FLT_MANT_DIG == 24 \ diff --git a/src/xdisp.c b/src/xdisp.c index 72d3bfa6398..398056144a8 100644 --- a/src/xdisp.c +++ b/src/xdisp.c @@ -12448,7 +12448,7 @@ display_echo_area (struct window *w) reset the echo_area_buffer in question to nil at the end because with_echo_area_buffer will set it to an empty buffer. */ bool i = display_last_displayed_message_p; - /* According to the C99, C11 and C++11 standards, the integral value + /* According to the C standard, the integral value of a "bool" is always 0 or 1, so this array access is safe here, if oddly typed. */ no_message_p = NILP (echo_area_buffer[i]);