Here
is the relevant part of C11 talking about inline function:
Any function with internal linkage
can be an inline function. For a function with external
linkage, the following restrictions
apply: If a function is declared with an inline
function specifier, then it shall
also be defined in the same translation unit. If all of the
file scope declarations for a
function in a translation unit include the inline function
specifier without extern, then the definition in that
translation unit is an inline
definition. An inline definition does not
provide an external definition for the function,
and does not forbid an external
definition in another translation unit. An inline definition
provides an alternative to an
external definition, which a translator may use to implement
any call to the function in the
same translation unit. It is unspecified whether a call to
the
function
uses the inline definition or the external definition.
EXAMPLE 1 The
declaration of an inline function with external linkage can
result in either an external
definition, or a
definition available for use only within the translation
unit. A file scope declaration with
extern
creates
an external definition. The following example shows an
entire translation unit.
inline double fahr(double t)
{
return (9.0 * t) / 5.0 + 32.0;
}
inline double cels(double t)
{
return
(5.0 * (t - 32.0)) / 9.0;
}
extern
double fahr(double); // creates an
external definition
double
convert(int is_fahr, double temp)
{
/*
A translator may
perform inline substitutions */
return
is_fahr ? cels(temp) : fahr(temp);
}
11 Note that the
definition of fahr
is
an external definition because fahr
is
also declared with extern, but
the definition of
cels
is
an inline definition. Because cels
has
external linkage and is referenced, an
external
definition has to appear in another translation unit (see
6.9); the inline definition and the external
definition are
distinct and either may be used for the call.
Yes in fact
gen_inline_functions just convert refferenced inline function
to normal function.
I have remove my changes (line 3042 & 3030) and just added
in gen_inline_functions around line 5597
if (file)
pstrcpy(file->filename, sizeof
file->filename, fn->filename);
sym->r = VT_SYM | VT_CONST;
sym->type.t &= ~VT_INLINE;
#ifdef _HACK
if (!(sym->type.t &
VT_EXTERN)) // extern inline = extern
sym->type.t |=
VT_STATIC; // else static
#endif
macro_ptr = str;
next();
cur_text_section = text_section;
I will do some test tomorrow
Pierre
Le 12/12/2013 00:27, Rob a écrit :
Odd, msvc isn't a C99 compiler, didn't
expect it to conform.
Anyway - I know the tcc code somewhat, but I'm not sure
about inline
functions. They're handled as sort-of-macros in some cases,
see
gen_inline_functions().
In short, I'm not sure of the changes and I'm off to bed
shortly. I do
think tcc should remain standard-compliant though, and not
imply static
or extern from just 'inline'. Perhaps we need another flag?
Rob
On Wed, 11 Dec 2013, Pierre wrote:
yes I think
you are right, it is same with msvc v6.
I don't know well the tcc code, but I don't think it inline
functions (like a macro, should be complicated to do).
So defining inline (alone) as static maybe a good idea ?
int tccgen.c line 3042
change:
case TOK_INLINE1:
case TOK_INLINE2:
case TOK_INLINE3:
t |= VT_INLINE;
next();
break;
to
case TOK_INLINE1:
case TOK_INLINE2:
case TOK_INLINE3:
if (!(t & VT_EXTERN)) //
if extern defined ignore 'inline'
t |= VT_INLINE | VT_STATIC; // if not
extern, set static as default
next();
break;
and line 3030
change
case TOK_EXTERN:
t |= VT_EXTERN;
to
case TOK_EXTERN:
{
t |= VT_EXTERN;
t &= ~VT_INLINE;
// remove 'inline'
}
I don't know if some more changes are required ?
Pierre
Le 11/12/2013 23:22, Rob a écrit :
'inline' alone should not generate code, I'm pretty
certain. It's an
inline-only definition. If it can't be inlined, you
get a linker error.
For example:
inline int f()
{
return 3;
}
int main()
{
return f();
}
A standalone function named 'f' will never appear in
the generated code.
If the compiler inlines 'f' into main, the program
will link. If the
compiler doesn't or can't inline 'f', you'll get a
linker error.
So we get a linker error with 'gcc -std=c99 -O0', but
the program links
fine with 'gcc -std=c99 -O1', as f isn't referenced
(since it's
inlined by an optimiser).
Also, I checked - gcc defaults to -std=gnu89, which
means gnu89 inline
semantics, so when testing, make sure you give it
'-std=c99'.
Clang exhibits the same behaviour w.r.t. inline, so
I'm pretty sure I've
interpreted the standard correctly. Note that clang
defaults to C99.
Thanks,
Rob
On Wed, 11 Dec 2013, Pierre wrote:
So inline alone should export nothing if not
refferenced (with code or forward declared), and at most,
create a static function if cannot be inlined ?
And an 'extern inline ' simply ignore 'inline' ?
Le 11/12/2013 22:33, Rob a écrit :
On Wed, 11 Dec 2013, Thomas Preud'homme
wrote:
Le mercredi 11 décembre 2013,
09:28:07 Christian JULLIEN a écrit :
I knew about the fact that it is a
hint and I knew even when inlined, the
function still needs to be output in
case its address is used. However I
forgot about the other details. I
stand corrected, thanks.
I remembered extern and inline has a
special meaning as well but I forgot so I
checked online and I think the
documentation of gcc [0] explains pretty well
how inline behave. I'm a bit
surprised though because I thought the special
meaning of extern inline was not in
the standard but something gcc specific.
Again, I stand corrected.
[0] http://gcc.gnu.org/onlinedocs/gcc/Inline.html
If you want to avoid problems
when you define an inlined function in a .h is
to declare this function
static. This way, if compiler is not able to
inline function, the two or
more translation units using it will have their
own static copy that will make
linker happy.
Or extern inline which has a
slightly different meaning. With static inline you
need to provide two implementation
of the function, one with static inline in
the header, and one normal
implementation somewhere else in case there is a
call that cannot be inlined or if
the address of the function is used. With
extern inline you make it clear that
you want the function inlined no matter
what. At least that is my
understanding after a quick read but again, I might
have read too quickly.
There are very subtle differences and with
gcc I'm pretty sure you have
to specify -std=c99 otherwise it defaults
to gnu89 which has different,
GNU inline semantics.
'inline', unfortunately is not just a hint
to the compiler. There are a
few checks compilers have to perform too.
So we have three forms of inline:
extern inline void func() { ... } // 1
static inline void func() { ... } // 2
inline void func() { ... } // 3
The first form, 'extern inline', will
always cause a
standalone/non-inlined function to be
emitted, just as if 'inline'
wasn't present. The inline modifier here
simply acts as a hint that this
function may be inlined.
The second form, 'static inline', will
cause function code to be
emitted, but the compiler may omit this if
it knows the function is
never used (since it's static, it's not
called from another translation
unit). Again, 'inline' acts only as a
hint.
The final form, 'inline' without a storage
class is where we have
special handling. In this case, standalone
function code is never
emitted, this version is _only_ to be used
for inline substitution.
For the final form to take affect, none of
the declarations of `func'
must mention extern, for example:
inline f();
inline f();
extern inline f(); // this causes `f' to
be in form 2
inline f() { ... }
At least, that's what I've gathered from
the standard and various
searches.
Thanks, Rob
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