On Thu, 2019-01-31 at 10:35 +0100, Richard Biener wrote:
> On Thu, Jan 31, 2019 at 12:09 AM David Malcolm <dmalc...@redhat.com>
> wrote:
> >
> > PR c/89122 reports that we emit a bogus fix-it hint for the case
> > where
> > the code uses FLT_MAX, but has included <limits.h> rather than
> > <float.h>:
> >
> > x.c:3:11: error: 'FLT_MAX' undeclared here (not in a function); did
> > you
> > mean 'INT_MAX'?
> > 3 | float f = FLT_MAX;
> > | ^~~~~~~
> > | INT_MAX
> >
> > This patch adds some knowledge of <float.h> (and <cfloat>) to
> > known-headers.cc, fixing the issue:
> >
> > x.c:3:11: error: 'FLT_MAX' undeclared here (not in a function)
> > 3 | float f = FLT_MAX;
> > | ^~~~~~~
> > x.c:2:1: note: 'FLT_MAX' is defined in header '<float.h>'; did you
> > forget
> > to '#include <float.h>'?
> > 1 | #include <limits.h>
> > +++ |+#include <float.h>
> > 2 |
> >
> > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
> >
> > Is this OK for trunk in stage 4? (presumably very low risk)
>
> What does it not say for
>
> int i = FLT_MAX;
>
> ? Hopefully it doesn't suggest to include float.h but suggests
> to include limits.h and INT_MAX?
The suggestions code (lookup_name_fuzzy) doesn't take types into
account, and has no knowledge of the "int-ness" of i. It's purely
looking for matches for names that it didn't recognize (albeit with an
enum to hint at whether it's looking for a type vs a function-like
thing vs "anything", but that wouldn't help here).
Trunk emits:
y.c:1:9: error: 'FLT_MAX' undeclared here (not in a function)
1 | int i = FLT_MAX;
| ^~~~~~~
With the patch it does indeed tell the user where FLT_MAX is:
y.c:1:9: error: 'FLT_MAX' undeclared here (not in a function)
1 | int i = FLT_MAX;
| ^~~~~~~
y.c:1:1: note: 'FLT_MAX' is defined in header '<float.h>'; did you
forget to '#include <float.h>'?
+++ |+#include <float.h>
1 | int i = FLT_MAX;
This doesn't seem too bad to me (in that it's screaming "float" to the
user); if the user ignores that and blindly follows the suggestion,
they get:
y.c:2:9: warning: overflow in conversion from 'float' to 'int' changes
value from '3.40282347e+38f' to '2147483647' [-Woverflow]
2 | int i = FLT_MAX;
| ^~~~~~~
y.c:2:1: warning: overflow in constant expression [-Woverflow]
2 | int i = FLT_MAX;
| ^~~
It's not clear to me that we would want a fix-it hint for this case
(where the compiler knows about FLT_MAX) - maybe the user meant to
write that? Such a fix-it hint might look something like:
y.c:2:9: warning: overflow in conversion from 'float' to 'int' changes
value from '3.40282347e+38f' to '2147483647'; did you mean 'INT_MAX' [-
Woverflow]
2 | int i = FLT_MAX;
| ^~~~~~~
| INT_MAX
...or somesuch, but that's clearly too ambitious a patch for stage 4.
Would that be reasonable for the next stage 1?
In the meantime, is the original patch OK?
Thanks
Dave
> > gcc/c-family/ChangeLog:
> > PR c/89122
> > * known-headers.cc (get_stdlib_header_for_name): Add
> > {FLT|DBL|LDBL}_{MAX|MIN} to "hints" array.
> >
> > gcc/testsuite/ChangeLog:
> > PR c/89122
> > * g++.dg/spellcheck-stdlib.C (test_FLT_MAX): New test.
> > * gcc.dg/spellcheck-stdlib.c (test_FLT_MAX): New test.
> > ---
> > gcc/c-family/known-headers.cc | 8 ++++++++
> > gcc/testsuite/g++.dg/spellcheck-stdlib.C | 5 +++++
> > gcc/testsuite/gcc.dg/spellcheck-stdlib.c | 5 +++++
> > 3 files changed, 18 insertions(+)
> >
> > diff --git a/gcc/c-family/known-headers.cc b/gcc/c-family/known-
> > headers.cc
> > index e3dcf73..c222f30 100644
> > --- a/gcc/c-family/known-headers.cc
> > +++ b/gcc/c-family/known-headers.cc
> > @@ -84,6 +84,14 @@ get_stdlib_header_for_name (const char *name,
> > enum stdlib lib)
> > {"ULONG_MAX", {"<limits.h>", "<climits>"} },
> > {"USHRT_MAX", {"<limits.h>", "<climits>"} },
> >
> > + /* <float.h> and <cfloat>. */
> > + {"DBL_MAX", {"<float.h>", "<cfloat>"} },
> > + {"DBL_MIN", {"<float.h>", "<cfloat>"} },
> > + {"FLT_MAX", {"<float.h>", "<cfloat>"} },
> > + {"FLT_MIN", {"<float.h>", "<cfloat>"} },
> > + {"LDBL_MAX", {"<float.h>", "<cfloat>"} },
> > + {"LDBL_MIN", {"<float.h>", "<cfloat>"} },
> > +
> > /* <stdarg.h> and <cstdarg>. */
> > {"va_list", {"<stdarg.h>", "<cstdarg>"} },
> >
> > diff --git a/gcc/testsuite/g++.dg/spellcheck-stdlib.C
> > b/gcc/testsuite/g++.dg/spellcheck-stdlib.C
> > index 11a4e3e..31e91fe 100644
> > --- a/gcc/testsuite/g++.dg/spellcheck-stdlib.C
> > +++ b/gcc/testsuite/g++.dg/spellcheck-stdlib.C
> > @@ -77,6 +77,11 @@ int test_INT_MAX (void)
> > // { dg-message "'INT_MAX' is defined in header '<climits>'; did
> > you forget to '#include <climits>'?" "" { target *-*-* }
> > INT_MAX_line }
> > }
> >
> > +/* Missing <cfloat>. */
> > +float test_FLT_MAX = FLT_MAX; // { dg-line FLT_MAX_line }
> > +// { dg-error "'FLT_MAX' was not declared" "" { target *-*-* }
> > FLT_MAX_line }
> > +// { dg-message "'FLT_MAX' is defined in header '<cfloat>'; did
> > you forget to '#include <cfloat>'?" "" { target *-*-* }
> > FLT_MAX_line }
> > +
> > /* Missing <cstring>. */
> >
> > void test_cstring (char *dest, char *src)
> > diff --git a/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
> > b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
> > index 7474c9a..1ae3b5e 100644
> > --- a/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
> > +++ b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
> > @@ -62,3 +62,8 @@ int test_INT_MAX (void)
> > /* { dg-bogus "__INT_MAX__" "" { target *-*-* } INT_MAX_line }
> > */
> > /* { dg-message "'INT_MAX' is defined in header '<limits.h>';
> > did you forget to '#include <limits.h>'?" "" { target *-*-* }
> > INT_MAX_line } */
> > }
> > +
> > +/* Missing <float.h>. */
> > +float test_FLT_MAX = FLT_MAX; /* { dg-line FLT_MAX_line } */
> > +/* { dg-error "'FLT_MAX' undeclared" "" { target *-*-* }
> > FLT_MAX_line } */
> > +/* { dg-message "'FLT_MAX' is defined in header '<float.h>'; did
> > you forget to '#include <float.h>'?" "" { target *-*-* }
> > FLT_MAX_line } */
> > --
> > 1.8.5.3
> >
