| Submitter | Florian Weimer |
|---|---|
| Date | Sept. 3, 2019, 10:12 a.m. |
| Message ID | <87lfv5sn6h.fsf@oldenburg2.str.redhat.com> |
| Download | mbox | patch |
| Permalink | /patch/34375/ |
| State | New |
| Headers | show |
Comments
On 03/09/2019 11:12, Florian Weimer wrote: > * Szabolcs Nagy: > >> On 30/08/2019 17:18, Florian Weimer wrote: >>> >>> localedef: Use initializer for flexible array member [BZ #24950] >>> >> >> i would mention that you put the struct in .rodata, >> that is a non-obvious change. > > Please see below. > >> i'm fine with using gcc extension for the initializer. >> i think the union solution is a bit safer though. >> either way, it would be nice to fix this build error. > > I don't think this is a GCC extension. I believe it's part of C99. iso c has this example: http://port70.net/~nsz/c/c11/n1570.html#6.7.2.1p21 so the initializer relies on a gcc extension. > > Thanks, > Florian > > localedef: Use initializer for flexible array member [BZ #24950] > > struct charseq used a zero-length array instead of a flexible array > member. This required a strange construct to initialize struct > charseq objects, and GCC 10 warns about that: > > cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=] > In file included from programs/repertoire.h:24, > from programs/localedef.h:32, > from programs/ld-ctype.c:35: > programs/charmap.h:63:17: note: destination object declared here > 63 | unsigned char bytes[0]; > | ^~~~~ > cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=] > programs/charmap.h:63:17: note: destination object declared here > cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=] > programs/charmap.h:63:17: note: destination object declared here > cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=] > programs/charmap.h:63:17: note: destination object declared here > > The change makes the object physically const, but it is not expected > to be modified. > > 2019-08-30 Florian Weimer <fweimer@redhat.com> > > [BZ #24950] > * locale/programs/charmap.h (struct charseq): Turn bytes into a > flexible array member. > * locale/programs/ld-ctype.c (ctype_finish): Use initializer for > replace. > > diff --git a/locale/programs/charmap.h b/locale/programs/charmap.h > index 870a9e9577..70db330d29 100644 > --- a/locale/programs/charmap.h > +++ b/locale/programs/charmap.h > @@ -60,7 +60,7 @@ struct charseq > const char *name; > uint32_t ucs4; > int nbytes; > - unsigned char bytes[0]; > + unsigned char bytes[]; > }; > > > diff --git a/locale/programs/ld-ctype.c b/locale/programs/ld-ctype.c > index cfc9c43fd5..9123f64a56 100644 > --- a/locale/programs/ld-ctype.c > +++ b/locale/programs/ld-ctype.c > @@ -842,8 +842,6 @@ no input digits defined and none of the standard names in the charmap")); > for (cnt = 0; cnt < 10; ++cnt) > if (ctype->mboutdigits[cnt] == NULL) > { > - static struct charseq replace[2]; > - > if (!warned) > { > record_error (0, 0, _("\ > @@ -851,10 +849,12 @@ not all characters used in `outdigit' are available in the charmap")); > warned = 1; > } > > - replace[0].nbytes = 1; > - replace[0].bytes[0] = '?'; > - replace[0].bytes[1] = '\0'; > - ctype->mboutdigits[cnt] = &replace[0]; > + static const struct charseq replace = > + { > + .nbytes = 1, > + .bytes = "?", > + }; > + ctype->mboutdigits[cnt] = (struct charseq *) &replace; > } > > warned = 0; >
On Sep 03 2019, Szabolcs Nagy <Szabolcs.Nagy@arm.com> wrote: > On 03/09/2019 11:12, Florian Weimer wrote: >> * Szabolcs Nagy: >> >>> On 30/08/2019 17:18, Florian Weimer wrote: >>>> >>>> localedef: Use initializer for flexible array member [BZ #24950] >>>> >>> >>> i would mention that you put the struct in .rodata, >>> that is a non-obvious change. >> >> Please see below. >> >>> i'm fine with using gcc extension for the initializer. >>> i think the union solution is a bit safer though. >>> either way, it would be nice to fix this build error. >> >> I don't think this is a GCC extension. I believe it's part of C99. > > iso c has this example: > > http://port70.net/~nsz/c/c11/n1570.html#6.7.2.1p21 > > so the initializer relies on a gcc extension. Which is documented in (gcc) Zero Length. Andreas.
* Szabolcs Nagy: > On 03/09/2019 11:12, Florian Weimer wrote: >> * Szabolcs Nagy: >> >>> On 30/08/2019 17:18, Florian Weimer wrote: >>>> >>>> localedef: Use initializer for flexible array member [BZ #24950] >>>> >>> >>> i would mention that you put the struct in .rodata, >>> that is a non-obvious change. >> >> Please see below. >> >>> i'm fine with using gcc extension for the initializer. >>> i think the union solution is a bit safer though. >>> either way, it would be nice to fix this build error. >> >> I don't think this is a GCC extension. I believe it's part of C99. > > iso c has this example: > > http://port70.net/~nsz/c/c11/n1570.html#6.7.2.1p21 > > so the initializer relies on a gcc extension. Okay, I stand corrected. What about the updated commit message I sent earlier? Shall I push this? Thanks, Florian
On 03/09/2019 11:53, Florian Weimer wrote: > * Szabolcs Nagy: > >> On 03/09/2019 11:12, Florian Weimer wrote: >>> * Szabolcs Nagy: >>> >>>> On 30/08/2019 17:18, Florian Weimer wrote: >>>>> >>>>> localedef: Use initializer for flexible array member [BZ #24950] >>>>> >>>> >>>> i would mention that you put the struct in .rodata, >>>> that is a non-obvious change. >>> >>> Please see below. >>> >>>> i'm fine with using gcc extension for the initializer. >>>> i think the union solution is a bit safer though. >>>> either way, it would be nice to fix this build error. >>> >>> I don't think this is a GCC extension. I believe it's part of C99. >> >> iso c has this example: >> >> http://port70.net/~nsz/c/c11/n1570.html#6.7.2.1p21 >> >> so the initializer relies on a gcc extension. > > Okay, I stand corrected. > > What about the updated commit message I sent earlier? Shall I push > this? i think the patch is ok as posted. > > Thanks, > Florian >
Patch
diff --git a/locale/programs/charmap.h b/locale/programs/charmap.h index 870a9e9577..70db330d29 100644 --- a/locale/programs/charmap.h +++ b/locale/programs/charmap.h @@ -60,7 +60,7 @@ struct charseq const char *name; uint32_t ucs4; int nbytes; - unsigned char bytes[0]; + unsigned char bytes[]; }; diff --git a/locale/programs/ld-ctype.c b/locale/programs/ld-ctype.c index cfc9c43fd5..9123f64a56 100644 --- a/locale/programs/ld-ctype.c +++ b/locale/programs/ld-ctype.c @@ -842,8 +842,6 @@ no input digits defined and none of the standard names in the charmap")); for (cnt = 0; cnt < 10; ++cnt) if (ctype->mboutdigits[cnt] == NULL) { - static struct charseq replace[2]; - if (!warned) { record_error (0, 0, _("\ @@ -851,10 +849,12 @@ not all characters used in `outdigit' are available in the charmap")); warned = 1; } - replace[0].nbytes = 1; - replace[0].bytes[0] = '?'; - replace[0].bytes[1] = '\0'; - ctype->mboutdigits[cnt] = &replace[0]; + static const struct charseq replace = + { + .nbytes = 1, + .bytes = "?", + }; + ctype->mboutdigits[cnt] = (struct charseq *) &replace; } warned = 0;