threads / patch / 38492

patchewah: fix building with gcc < 3.4.0

Subject: [PATCH] ewah: fix building with gcc < 3.4.0

## tl;dr

4 messages between Feb 3, 2015 and Feb 4, 2015. Diffs are folded; open one to read it.

replies: 3people: 3as markdown or json

Tom G. Christensen· Feb 3, 2015, 10:27 UTC · lore

The __builtin_ctzll function was added in gcc 3.4.0. This extends the check for gcc so that use of __builtin_ctzll is only enabled if gcc >= 3.4.0. ---

I noticed this on RHEL3 during 2.0.0rc phase but I see that the same issue was noticed on Debian Sarge: http://article.gmane.org/gmane.comp.version-control.git/255190 RHEL3 ships with gcc 3.2.3.

With this patch git can build on RHEL3 provided cURL support is disabled.
 ewah/ewok.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
Show changes to ewah/ewok.h +2 −1
diff --git a/ewah/ewok.h b/ewah/ewok.h
index f6ad190..13c6e20 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -47,7 +47,8 @@ static inline uint32_t ewah_bit_popcount64(uint64_t x)
 	return (x * 0x0101010101010101ULL) >> 56;
 }
 
-#ifdef __GNUC__
+/* __builtin_ctzll was not available until 3.4.0 */
+#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3  && __GNUC_MINOR > 3))
 #define ewah_bit_ctz64(x) __builtin_ctzll(x)
 #else
 static inline int ewah_bit_ctz64(uint64_t x)

-- 
2.2.2
Jeff King· Feb 3, 2015, 16:35 UTC · re: Tom G. Christensen · lore

Re: [PATCH] ewah: fix building with gcc < 3.4.0

On Tue, Feb 03, 2015 at 11:27:07AM +0100, Tom G. Christensen wrote:
Show 11 quoted lines
> The __builtin_ctzll function was added in gcc 3.4.0.
> This extends the check for gcc so that use of __builtin_ctzll is only
> enabled if gcc >= 3.4.0.
> ---
> 
> I noticed this on RHEL3 during 2.0.0rc phase but I see that the same
> issue was noticed on Debian Sarge:
> http://article.gmane.org/gmane.comp.version-control.git/255190
> RHEL3 ships with gcc 3.2.3.
> 
> With this patch git can build on RHEL3 provided cURL support is disabled.

Thanks. I built with some older gcc's at the time this was developed, but I don't think I went past what was in Debian stable, which was probably 4.something.

Show 6 quoted lines
> -#ifdef __GNUC__
> +/* __builtin_ctzll was not available until 3.4.0 */
> +#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3  && __GNUC_MINOR > 3))
>  #define ewah_bit_ctz64(x) __builtin_ctzll(x)
>  #else
>  static inline int ewah_bit_ctz64(uint64_t x)

We could turn this into a HAS_CTZLL Makefile knob (and auto-set it as above), but I don't think it is worth it. I don't expect anybody to need to tweak it. I double-checked that clang sets the value of __GNUC__ appropriately.

-Peff
Junio C Hamano· Feb 3, 2015, 21:48 UTC · re: Jeff King · lore

Re: [PATCH] ewah: fix building with gcc < 3.4.0

Jeff King <peff@peff.net> writes:
Show 29 quoted lines
> On Tue, Feb 03, 2015 at 11:27:07AM +0100, Tom G. Christensen wrote:
>
>> The __builtin_ctzll function was added in gcc 3.4.0.
>> This extends the check for gcc so that use of __builtin_ctzll is only
>> enabled if gcc >= 3.4.0.
>> ---
>> 
>> I noticed this on RHEL3 during 2.0.0rc phase but I see that the same
>> issue was noticed on Debian Sarge:
>> http://article.gmane.org/gmane.comp.version-control.git/255190
>> RHEL3 ships with gcc 3.2.3.
>> 
>> With this patch git can build on RHEL3 provided cURL support is disabled.
>
> Thanks. I built with some older gcc's at the time this was developed,
> but I don't think I went past what was in Debian stable, which was
> probably 4.something.
>
>> -#ifdef __GNUC__
>> +/* __builtin_ctzll was not available until 3.4.0 */
>> +#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3  && __GNUC_MINOR > 3))
>>  #define ewah_bit_ctz64(x) __builtin_ctzll(x)
>>  #else
>>  static inline int ewah_bit_ctz64(uint64_t x)
>
> We could turn this into a HAS_CTZLL Makefile knob (and auto-set it as
> above), but I don't think it is worth it. I don't expect anybody to need
> to tweak it. I double-checked that clang sets the value of __GNUC__
> appropriately.

OK. I would imagine that this would go on top of jk/pack-bitmap, which we could be merged down to 2.0.x maintenance track if we wanted to.

Tom, can you make it a habit to sign-off your patch?
Tom G. Christensen· Feb 4, 2015, 08:23 UTC · re: Junio C Hamano · lore

[PATCH v2] ewah: fix building with gcc < 3.4.0

The __builtin_ctzll function was added in gcc 3.4.0. This extends the check for gcc so that use of __builtin_ctzll is only enabled if gcc >= 3.4.0.

Signed-off-by: Tom G. Christensen <tgc@statsbiblioteket.dk>
---
v2:
Add S-o-b

v1: I noticed this on RHEL3 during 2.0.0rc phase but I see that the same issue was noticed on Debian Sarge: http://article.gmane.org/gmane.comp.version-control.git/255190 RHEL3 ships with gcc 3.2.3.

With this patch git can build on RHEL3 provided cURL support is disabled.
 ewah/ewok.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
Show changes to ewah/ewok.h +2 −1
diff --git a/ewah/ewok.h b/ewah/ewok.h
index f6ad190..13c6e20 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -47,7 +47,8 @@ static inline uint32_t ewah_bit_popcount64(uint64_t x)
 	return (x * 0x0101010101010101ULL) >> 56;
 }
 
-#ifdef __GNUC__
+/* __builtin_ctzll was not available until 3.4.0 */
+#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3  && __GNUC_MINOR > 3))
 #define ewah_bit_ctz64(x) __builtin_ctzll(x)
 #else
 static inline int ewah_bit_ctz64(uint64_t x)

-- 
2.2.2

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