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doc: Fix documentation around 'asm' keyword in C++

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The documentation on asm statements suggests asm is always a GNU
extension, but it's been part of ISO C++ since the first standard.

The documentation of -fno-asm is wrong for C++ as it states that it only
affects typeof, but actually it affects typeof and asm (despite asm
being part of ISO C++).

gcc/ChangeLog:

	* doc/extend.texi (Basic Asm): Clarify that asm is not an
	extension in C++.
	* doc/invoke.texi (-fno-asm): Fix description for C++.
This commit is contained in:
Jonathan Wakely 2021-10-20 19:41:49 +01:00
parent 885f9b4ad5
commit 154c6d430e
2 changed files with 13 additions and 11 deletions
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10
gcc/doc/extend.texi
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@ -9728,10 +9728,12 @@ A basic @code{asm} statement has the following syntax:
asm @var{asm-qualifiers} ( @var{AssemblerInstructions} )
@end example
The @code{asm} keyword is a GNU extension.
When writing code that can be compiled with @option{-ansi} and the
various @option{-std} options, use @code{__asm__} instead of
@code{asm} (@pxref{Alternate Keywords}).
For the C language, the @code{asm} keyword is a GNU extension.
When writing C code that can be compiled with @option{-ansi} and the
@option{-std} options that select C dialects without GNU extensions, use
@code{__asm__} instead of @code{asm} (@pxref{Alternate Keywords}). For
the C++ language, @code{asm} is a standard keyword, but @code{__asm__}
can be used for code compiled with @option{-fno-asm}.
@subsubheading Qualifiers
@table @code

14
gcc/doc/invoke.texi
View file

@ -2485,14 +2485,14 @@ supported for C as this construct is allowed by C++.
Do not recognize @code{asm}, @code{inline} or @code{typeof} as a
keyword, so that code can use these words as identifiers. You can use
the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__}
instead. @option{-ansi} implies @option{-fno-asm}.
instead. In C, @option{-ansi} implies @option{-fno-asm}.
In C++, this switch only affects the @code{typeof} keyword, since
@code{asm} and @code{inline} are standard keywords. You may want to
use the @option{-fno-gnu-keywords} flag instead, which has the same
effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this
switch only affects the @code{asm} and @code{typeof} keywords, since
@code{inline} is a standard keyword in ISO C99.
In C++, @code{inline} is a standard keyword and is not affected by
this switch. You may want to use the @option{-fno-gnu-keywords} flag
instead, which disables @code{typeof} but not @code{asm} and
@code{inline}. In C99 mode (@option{-std=c99} or @option{-std=gnu99}),
this switch only affects the @code{asm} and @code{typeof} keywords,
since @code{inline} is a standard keyword in ISO C99.
@item -fno-builtin
@itemx -fno-builtin-@var{function}