| Message ID | alpine.LNX.2.00.1201090956060.4999@zhemvz.fhfr.qr |
|---|---|
| State | New |
| Headers | show |
It looks non-ambiguous to me. David On Mon, Jan 9, 2012 at 1:05 AM, Richard Guenther <rguenther@suse.de> wrote: > > Since GCC 4.4 applying the malloc attribute to realloc-like > functions does not work under the documented constraints because > the contents of the memory pointed to are not properly transfered > from the realloc argument (or treated as pointing to anything, > like 4.3 behaved). > > The following adjusts documentation to reflect implementation > reality (we do have an implementation detail that treats the > memory blob returned for non-builtins as pointing to any global > variable, but that is neither documented nor do I plan to do > so - I presume it is to allow allocation + initialization > routines to be marked with malloc, but even that area looks > susceptible to misinterpretation to me). > > Any comments? > > Thanks, > Richard. > > 2012-01-09 Richard Guenther <rguenther@suse.de> > > * doc/extend.texi (malloc attribute): Adjust according to > implementation. > > Index: gcc/doc/extend.texi > =================================================================== > --- gcc/doc/extend.texi (revision 183001) > +++ gcc/doc/extend.texi (working copy) > @@ -2771,13 +2771,12 @@ efficient @code{jal} instruction. > @cindex @code{malloc} attribute > The @code{malloc} attribute is used to tell the compiler that a function > may be treated as if any non-@code{NULL} pointer it returns cannot > -alias any other pointer valid when the function returns. > +alias any other pointer valid when the function returns and that the memory > +has undefined content. > This will often improve optimization. > Standard functions with this property include @code{malloc} and > -@code{calloc}. @code{realloc}-like functions have this property as > -long as the old pointer is never referred to (including comparing it > -to the new pointer) after the function returns a non-@code{NULL} > -value. > +@code{calloc}. @code{realloc}-like functions do not have this > +property as the memory pointed to does not have undefined content. > > @item mips16/nomips16 > @cindex @code{mips16} attribute
On Mon, 9 Jan 2012, Xinliang David Li wrote: > It looks non-ambiguous to me. The new proposed version or the old? Richard. > David > > On Mon, Jan 9, 2012 at 1:05 AM, Richard Guenther <rguenther@suse.de> wrote: > > > > Since GCC 4.4 applying the malloc attribute to realloc-like > > functions does not work under the documented constraints because > > the contents of the memory pointed to are not properly transfered > > from the realloc argument (or treated as pointing to anything, > > like 4.3 behaved). > > > > The following adjusts documentation to reflect implementation > > reality (we do have an implementation detail that treats the > > memory blob returned for non-builtins as pointing to any global > > variable, but that is neither documented nor do I plan to do > > so - I presume it is to allow allocation + initialization > > routines to be marked with malloc, but even that area looks > > susceptible to misinterpretation to me). > > > > Any comments? > > > > Thanks, > > Richard. > > > > 2012-01-09 Richard Guenther <rguenther@suse.de> > > > > * doc/extend.texi (malloc attribute): Adjust according to > > implementation. > > > > Index: gcc/doc/extend.texi > > =================================================================== > > --- gcc/doc/extend.texi (revision 183001) > > +++ gcc/doc/extend.texi (working copy) > > @@ -2771,13 +2771,12 @@ efficient @code{jal} instruction. > > @cindex @code{malloc} attribute > > The @code{malloc} attribute is used to tell the compiler that a function > > may be treated as if any non-@code{NULL} pointer it returns cannot > > -alias any other pointer valid when the function returns. > > +alias any other pointer valid when the function returns and that the memory > > +has undefined content. > > This will often improve optimization. > > Standard functions with this property include @code{malloc} and > > -@code{calloc}. @code{realloc}-like functions have this property as > > -long as the old pointer is never referred to (including comparing it > > -to the new pointer) after the function returns a non-@code{NULL} > > -value. > > +@code{calloc}. @code{realloc}-like functions do not have this > > +property as the memory pointed to does not have undefined content. > > > > @item mips16/nomips16 > > @cindex @code{mips16} attribute > >
of course your new version. thanks, David On Tue, Jan 10, 2012 at 1:31 AM, Richard Guenther <rguenther@suse.de> wrote: > On Mon, 9 Jan 2012, Xinliang David Li wrote: > >> It looks non-ambiguous to me. > > The new proposed version or the old? > > Richard. > >> David >> >> On Mon, Jan 9, 2012 at 1:05 AM, Richard Guenther <rguenther@suse.de> wrote: >> > >> > Since GCC 4.4 applying the malloc attribute to realloc-like >> > functions does not work under the documented constraints because >> > the contents of the memory pointed to are not properly transfered >> > from the realloc argument (or treated as pointing to anything, >> > like 4.3 behaved). >> > >> > The following adjusts documentation to reflect implementation >> > reality (we do have an implementation detail that treats the >> > memory blob returned for non-builtins as pointing to any global >> > variable, but that is neither documented nor do I plan to do >> > so - I presume it is to allow allocation + initialization >> > routines to be marked with malloc, but even that area looks >> > susceptible to misinterpretation to me). >> > >> > Any comments? >> > >> > Thanks, >> > Richard. >> > >> > 2012-01-09 Richard Guenther <rguenther@suse.de> >> > >> > * doc/extend.texi (malloc attribute): Adjust according to >> > implementation. >> > >> > Index: gcc/doc/extend.texi >> > =================================================================== >> > --- gcc/doc/extend.texi (revision 183001) >> > +++ gcc/doc/extend.texi (working copy) >> > @@ -2771,13 +2771,12 @@ efficient @code{jal} instruction. >> > @cindex @code{malloc} attribute >> > The @code{malloc} attribute is used to tell the compiler that a function >> > may be treated as if any non-@code{NULL} pointer it returns cannot >> > -alias any other pointer valid when the function returns. >> > +alias any other pointer valid when the function returns and that the memory >> > +has undefined content. >> > This will often improve optimization. >> > Standard functions with this property include @code{malloc} and >> > -@code{calloc}. @code{realloc}-like functions have this property as >> > -long as the old pointer is never referred to (including comparing it >> > -to the new pointer) after the function returns a non-@code{NULL} >> > -value. >> > +@code{calloc}. @code{realloc}-like functions do not have this >> > +property as the memory pointed to does not have undefined content. >> > >> > @item mips16/nomips16 >> > @cindex @code{mips16} attribute >> >> > > -- > Richard Guenther <rguenther@suse.de> > SUSE / SUSE Labs > SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
On Tue, 10 Jan 2012, Xinliang David Li wrote: > of course your new version. I have installed it on the trunk. Richard. > thanks, > > David > > On Tue, Jan 10, 2012 at 1:31 AM, Richard Guenther <rguenther@suse.de> wrote: > > On Mon, 9 Jan 2012, Xinliang David Li wrote: > > > >> It looks non-ambiguous to me. > > > > The new proposed version or the old? > > > > Richard. > > > >> David > >> > >> On Mon, Jan 9, 2012 at 1:05 AM, Richard Guenther <rguenther@suse.de> wrote: > >> > > >> > Since GCC 4.4 applying the malloc attribute to realloc-like > >> > functions does not work under the documented constraints because > >> > the contents of the memory pointed to are not properly transfered > >> > from the realloc argument (or treated as pointing to anything, > >> > like 4.3 behaved). > >> > > >> > The following adjusts documentation to reflect implementation > >> > reality (we do have an implementation detail that treats the > >> > memory blob returned for non-builtins as pointing to any global > >> > variable, but that is neither documented nor do I plan to do > >> > so - I presume it is to allow allocation + initialization > >> > routines to be marked with malloc, but even that area looks > >> > susceptible to misinterpretation to me). > >> > > >> > Any comments? > >> > > >> > Thanks, > >> > Richard. > >> > > >> > 2012-01-09 Richard Guenther <rguenther@suse.de> > >> > > >> > * doc/extend.texi (malloc attribute): Adjust according to > >> > implementation. > >> > > >> > Index: gcc/doc/extend.texi > >> > =================================================================== > >> > --- gcc/doc/extend.texi (revision 183001) > >> > +++ gcc/doc/extend.texi (working copy) > >> > @@ -2771,13 +2771,12 @@ efficient @code{jal} instruction. > >> > @cindex @code{malloc} attribute > >> > The @code{malloc} attribute is used to tell the compiler that a function > >> > may be treated as if any non-@code{NULL} pointer it returns cannot > >> > -alias any other pointer valid when the function returns. > >> > +alias any other pointer valid when the function returns and that the memory > >> > +has undefined content. > >> > This will often improve optimization. > >> > Standard functions with this property include @code{malloc} and > >> > -@code{calloc}. @code{realloc}-like functions have this property as > >> > -long as the old pointer is never referred to (including comparing it > >> > -to the new pointer) after the function returns a non-@code{NULL} > >> > -value. > >> > +@code{calloc}. @code{realloc}-like functions do not have this > >> > +property as the memory pointed to does not have undefined content. > >> > > >> > @item mips16/nomips16 > >> > @cindex @code{mips16} attribute > >> > >> > > > > -- > > Richard Guenther <rguenther@suse.de> > > SUSE / SUSE Labs > > SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 > > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer > >
Index: gcc/doc/extend.texi =================================================================== --- gcc/doc/extend.texi (revision 183001) +++ gcc/doc/extend.texi (working copy) @@ -2771,13 +2771,12 @@ efficient @code{jal} instruction. @cindex @code{malloc} attribute The @code{malloc} attribute is used to tell the compiler that a function may be treated as if any non-@code{NULL} pointer it returns cannot -alias any other pointer valid when the function returns. +alias any other pointer valid when the function returns and that the memory +has undefined content. This will often improve optimization. Standard functions with this property include @code{malloc} and -@code{calloc}. @code{realloc}-like functions have this property as -long as the old pointer is never referred to (including comparing it -to the new pointer) after the function returns a non-@code{NULL} -value. +@code{calloc}. @code{realloc}-like functions do not have this +property as the memory pointed to does not have undefined content. @item mips16/nomips16 @cindex @code{mips16} attribute