* [PATCH] Rewrite gdb_mpz::operator==
@ 2023-04-19 15:09 Tom Tromey
2023-04-19 16:23 ` Simon Marchi
0 siblings, 1 reply; 7+ messages in thread
From: Tom Tromey @ 2023-04-19 15:09 UTC (permalink / raw)
To: gdb-patches; +Cc: Tom Tromey
Simon pointed out that the recent changes to gdb_mpz caused a build
failure on macOS. It turns out to be somewhat difficult to overload a
method in a way that will work "naturally" for all integer types;
especially in a case like gdb_mpz::operator==, where it's desirable to
special case all integer types that are no wider than 'long'.
After a false start, I came up with this patch, which seems to work.
It applies the desirable GMP special cases directly in the body,
rather than via overloads.
---
gdb/gmp-utils.h | 38 ++++++++++++++------------------------
1 file changed, 14 insertions(+), 24 deletions(-)
diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
index d05c11ecbe4..3586d01b0f9 100644
--- a/gdb/gmp-utils.h
+++ b/gdb/gmp-utils.h
@@ -323,31 +323,21 @@ struct gdb_mpz
return mpz_cmp_si (m_val, other) < 0;
}
- bool operator== (int other) const
- {
- return mpz_cmp_si (m_val, other) == 0;
- }
-
- bool operator== (long other) const
- {
- return mpz_cmp_si (m_val, other) == 0;
- }
-
- bool operator== (unsigned long other) const
- {
- return mpz_cmp_ui (m_val, other) == 0;
- }
-
template<typename T,
- typename = gdb::Requires<
- gdb::And<std::is_integral<T>,
- std::integral_constant<bool,
- (sizeof (T) > sizeof (long))>>
- >
- >
- bool operator== (T src)
- {
- return *this == gdb_mpz (src);
+ typename = gdb::Requires<std::is_integral<T>>>
+ bool operator== (T other) const
+ {
+ if (std::is_signed<T>::value)
+ {
+ if (other == (T) (long) other)
+ return mpz_cmp_si (m_val, other) == 0;
+ }
+ else
+ {
+ if (other == (T) (unsigned long) other)
+ return mpz_cmp_ui (m_val, other) == 0;
+ }
+ return *this == gdb_mpz (other);
}
bool operator== (const gdb_mpz &other) const
--
2.39.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-19 15:09 [PATCH] Rewrite gdb_mpz::operator== Tom Tromey
@ 2023-04-19 16:23 ` Simon Marchi
2023-04-21 13:00 ` Tom Tromey
0 siblings, 1 reply; 7+ messages in thread
From: Simon Marchi @ 2023-04-19 16:23 UTC (permalink / raw)
To: Tom Tromey, gdb-patches
On 4/19/23 11:09, Tom Tromey via Gdb-patches wrote:
> Simon pointed out that the recent changes to gdb_mpz caused a build
> failure on macOS. It turns out to be somewhat difficult to overload a
For some reason, just macOS on amd64, not arm64.
> method in a way that will work "naturally" for all integer types;
> especially in a case like gdb_mpz::operator==, where it's desirable to
> special case all integer types that are no wider than 'long'.
>
> After a false start, I came up with this patch, which seems to work.
> It applies the desirable GMP special cases directly in the body,
> rather than via overloads.
> ---
> gdb/gmp-utils.h | 38 ++++++++++++++------------------------
> 1 file changed, 14 insertions(+), 24 deletions(-)
>
> diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
> index d05c11ecbe4..3586d01b0f9 100644
> --- a/gdb/gmp-utils.h
> +++ b/gdb/gmp-utils.h
> @@ -323,31 +323,21 @@ struct gdb_mpz
> return mpz_cmp_si (m_val, other) < 0;
> }
>
> - bool operator== (int other) const
> - {
> - return mpz_cmp_si (m_val, other) == 0;
> - }
> -
> - bool operator== (long other) const
> - {
> - return mpz_cmp_si (m_val, other) == 0;
> - }
> -
> - bool operator== (unsigned long other) const
> - {
> - return mpz_cmp_ui (m_val, other) == 0;
> - }
> -
> template<typename T,
> - typename = gdb::Requires<
> - gdb::And<std::is_integral<T>,
> - std::integral_constant<bool,
> - (sizeof (T) > sizeof (long))>>
> - >
> - >
> - bool operator== (T src)
> - {
> - return *this == gdb_mpz (src);
> + typename = gdb::Requires<std::is_integral<T>>>
> + bool operator== (T other) const
> + {
> + if (std::is_signed<T>::value)
> + {
> + if (other == (T) (long) other)
It's a bit hard to understand what the intent is, if you don't know the
problematic already. Could you add a comment explaining that?
Also, wouldn't it work to compare size? Like:
if (sizeof (T) <= sizeof (long))
Simon
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-19 16:23 ` Simon Marchi
@ 2023-04-21 13:00 ` Tom Tromey
2023-04-21 13:13 ` Simon Marchi
0 siblings, 1 reply; 7+ messages in thread
From: Tom Tromey @ 2023-04-21 13:00 UTC (permalink / raw)
To: Simon Marchi; +Cc: Tom Tromey, gdb-patches
>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:
Simon> It's a bit hard to understand what the intent is, if you don't know the
Simon> problematic already. Could you add a comment explaining that?
Sure.
Simon> Also, wouldn't it work to compare size? Like:
Simon> if (sizeof (T) <= sizeof (long))
Yeah, though I was concerned that the compiler might emit warnings about
always-true conditions in this case.
Tom
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-21 13:00 ` Tom Tromey
@ 2023-04-21 13:13 ` Simon Marchi
2023-04-21 15:02 ` Tom Tromey
0 siblings, 1 reply; 7+ messages in thread
From: Simon Marchi @ 2023-04-21 13:13 UTC (permalink / raw)
To: Tom Tromey; +Cc: gdb-patches
On 4/21/23 09:00, Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:
>
> Simon> It's a bit hard to understand what the intent is, if you don't know the
> Simon> problematic already. Could you add a comment explaining that?
>
> Sure.
>
> Simon> Also, wouldn't it work to compare size? Like:
> Simon> if (sizeof (T) <= sizeof (long))
>
> Yeah, though I was concerned that the compiler might emit warnings about
> always-true conditions in this case.
Well, that would be surprising for code in a template, where T is not
know in advance.
Simon
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-21 13:13 ` Simon Marchi
@ 2023-04-21 15:02 ` Tom Tromey
2023-04-24 16:31 ` Tom Tromey
0 siblings, 1 reply; 7+ messages in thread
From: Tom Tromey @ 2023-04-21 15:02 UTC (permalink / raw)
To: Simon Marchi; +Cc: Tom Tromey, gdb-patches
>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:
>> Yeah, though I was concerned that the compiler might emit warnings about
>> always-true conditions in this case.
Simon> Well, that would be surprising for code in a template, where T is not
Simon> know in advance.
I feel like it happened in the past, but maybe it doesn't any more.
I'll rewrite this patch.
Tom
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-21 15:02 ` Tom Tromey
@ 2023-04-24 16:31 ` Tom Tromey
2023-04-25 18:55 ` Simon Marchi
0 siblings, 1 reply; 7+ messages in thread
From: Tom Tromey @ 2023-04-24 16:31 UTC (permalink / raw)
To: Tom Tromey; +Cc: Simon Marchi, gdb-patches
Tom> I feel like it happened in the past, but maybe it doesn't any more.
Tom> I'll rewrite this patch.
Here's v3.
Tom
commit f12c9b23d3ac219e08818935930f5ee891396158
Author: Tom Tromey <tromey@adacore.com>
Date: Mon Apr 17 12:59:57 2023 -0600
Rewrite gdb_mpz::operator==
Simon pointed out that the recent changes to gdb_mpz caused a build
failure on amd64 macOS. It turns out to be somewhat difficult to
overload a method in a way that will work "naturally" for all integer
types; especially in a case like gdb_mpz::operator==, where it's
desirable to special case all integer types that are no wider than
'long'.
After a false start, I came up with this patch, which seems to work.
It applies the desirable GMP special cases directly in the body,
rather than via overloads.
diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
index d05c11ecbe4..1bbdd9564fa 100644
--- a/gdb/gmp-utils.h
+++ b/gdb/gmp-utils.h
@@ -323,31 +323,26 @@ struct gdb_mpz
return mpz_cmp_si (m_val, other) < 0;
}
- bool operator== (int other) const
- {
- return mpz_cmp_si (m_val, other) == 0;
- }
-
- bool operator== (long other) const
- {
- return mpz_cmp_si (m_val, other) == 0;
- }
-
- bool operator== (unsigned long other) const
- {
- return mpz_cmp_ui (m_val, other) == 0;
- }
-
+ /* We want an operator== that can handle all integer types. For
+ types that are 'long' or narrower, we can use a GMP function and
+ avoid boxing the RHS. But, because overloading based on integer
+ type is a pain in C++, we accept all such types here and check
+ the size in the body. */
template<typename T,
- typename = gdb::Requires<
- gdb::And<std::is_integral<T>,
- std::integral_constant<bool,
- (sizeof (T) > sizeof (long))>>
- >
- >
- bool operator== (T src)
- {
- return *this == gdb_mpz (src);
+ typename = gdb::Requires<std::is_integral<T>>>
+ bool operator== (T other) const
+ {
+ if (std::is_signed<T>::value)
+ {
+ if (sizeof (T) <= sizeof (long))
+ return mpz_cmp_si (m_val, other) == 0;
+ }
+ else
+ {
+ if (sizeof (T) <= sizeof (unsigned long))
+ return mpz_cmp_ui (m_val, other) == 0;
+ }
+ return *this == gdb_mpz (other);
}
bool operator== (const gdb_mpz &other) const
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] Rewrite gdb_mpz::operator==
2023-04-24 16:31 ` Tom Tromey
@ 2023-04-25 18:55 ` Simon Marchi
0 siblings, 0 replies; 7+ messages in thread
From: Simon Marchi @ 2023-04-25 18:55 UTC (permalink / raw)
To: Tom Tromey; +Cc: gdb-patches
> diff --git a/gdb/gmp-utils.h b/gdb/gmp-utils.h
> index d05c11ecbe4..1bbdd9564fa 100644
> --- a/gdb/gmp-utils.h
> +++ b/gdb/gmp-utils.h
> @@ -323,31 +323,26 @@ struct gdb_mpz
> return mpz_cmp_si (m_val, other) < 0;
> }
>
> - bool operator== (int other) const
> - {
> - return mpz_cmp_si (m_val, other) == 0;
> - }
> -
> - bool operator== (long other) const
> - {
> - return mpz_cmp_si (m_val, other) == 0;
> - }
> -
> - bool operator== (unsigned long other) const
> - {
> - return mpz_cmp_ui (m_val, other) == 0;
> - }
> -
> + /* We want an operator== that can handle all integer types. For
> + types that are 'long' or narrower, we can use a GMP function and
> + avoid boxing the RHS. But, because overloading based on integer
> + type is a pain in C++, we accept all such types here and check
> + the size in the body. */
> template<typename T,
> - typename = gdb::Requires<
> - gdb::And<std::is_integral<T>,
> - std::integral_constant<bool,
> - (sizeof (T) > sizeof (long))>>
> - >
> - >
> - bool operator== (T src)
> - {
> - return *this == gdb_mpz (src);
> + typename = gdb::Requires<std::is_integral<T>>>
The template expression would fit on a single line, if you'd prefer to
write it that way.
Otherwise, LGTM. I think it's now relatively clear what the code tries
to achieve.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Simon
^ permalink raw reply [flat|nested] 7+ messages in thread
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2023-04-19 15:09 [PATCH] Rewrite gdb_mpz::operator== Tom Tromey
2023-04-19 16:23 ` Simon Marchi
2023-04-21 13:00 ` Tom Tromey
2023-04-21 13:13 ` Simon Marchi
2023-04-21 15:02 ` Tom Tromey
2023-04-24 16:31 ` Tom Tromey
2023-04-25 18:55 ` Simon Marchi
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