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Re: [Tinycc-devel] RE :Re: inline functions

From: Pierre
Subject: Re: [Tinycc-devel] RE :Re: inline functions
Date: Thu, 12 Dec 2013 09:29:45 +0100
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

I have tested the changes in gen_inline_functions but do not work.
I have made change in decl0() in tccgen around line 5706

                while ((sym = sym->next) != NULL)
                    if (!(sym->v & ~SYM_FIELD))
#ifdef _HACK
                if (type.t & VT_INLINE)
                  if (type.t & VT_EXTERN)
                    type.t &= ~VT_INLINE;
                    type.t |= VT_STATIC;
                /* XXX: cannot do better now: convert extern inline to static inline */
                if ((type.t & (VT_EXTERN | VT_INLINE)) == (VT_EXTERN | VT_INLINE))
                    type.t = (type.t & ~VT_EXTERN) | VT_STATIC;
                sym = sym_find(v);
                if (sym) {
                    if ((sym->type.t & VT_BTYPE) != VT_FUNC)
                        goto func_error1;

this works to link my project with inline code in .h

Le 12/12/2013 06:45, Christian Jullien a écrit :

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.




From: address@hidden [mailto:address@hidden] On Behalf Of Pierre
Sent: jeudi 12 décembre 2013 00:48
To: address@hidden
Subject: Re: [Tinycc-devel] RE :Re: inline functions


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
                macro_ptr = str;
                cur_text_section = text_section;

I will do some test tomorrow

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

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?


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


        case TOK_INLINE1:
        case TOK_INLINE2:
        case TOK_INLINE3:
            t |= VT_INLINE;


        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

and line 3030

        case TOK_EXTERN:
            t |= VT_EXTERN;

        case TOK_EXTERN:
            t |= VT_EXTERN;
            t &= ~VT_INLINE;                            // remove 'inline'

I don't know if some more changes are required ?

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.


      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

                  Thanks, Rob

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