diff mbox

[1/1] protobuf: fix detection of __atomic_*() built-ins

Message ID 1455118392-3965-1-git-send-email-casantos@datacom.ind.br
State Superseded
Headers show

Commit Message

Carlos Santos Feb. 10, 2016, 3:33 p.m. UTC 
- Use the recently introduced BR2_TOOLCHAIN_HAS_ATOMIC boolean.

- Import an upstream patch to fix error handling when atomic operations
  are not detected. Without this patch the build fails due to a syntax
  error instead of showing the proper message.

- Add a patch to configure.ac to check if libatomic is needed and force
  linking to it (this patch would unlikely be accepted upstream).

On PowerPC, the __atomic_*() built-ins for 1-byte, 2-byte and 4-byte
types are available built-in. However, the __atomic_*() built-ins for
8-byte types is implemented via libatomic, so only available since gcc
4.8.

In Buildroot, to simplify things, we've decided to simply require gcc 4.8
as soon as the architectures has at least one __atomic_*() built-in
variant that requires libatomic.

Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
*could* technically build with gcc 4.7. This is probably not a big deal,
and we can live with requiring gcc 4.8 on PowerPC to build protobuf.

Signed-off-by: Henrique Marks <henrique.marks@datacom.ind.br>
Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
---
 ...GLE_PROTOBUF_ATOMICOPS_ERROR-syntax-error.patch | 61 ++++++++++++++++++++++
 ...configure.ac-check-if-libatomic-is-needed.patch | 34 ++++++++++++
 package/protobuf/Config.in                         | 20 +++++--
 3 files changed, 110 insertions(+), 5 deletions(-)
 create mode 100644 package/protobuf/0001-Fix-GOOGLE_PROTOBUF_ATOMICOPS_ERROR-syntax-error.patch
 create mode 100644 package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch

Comments

Thomas Petazzoni Feb. 10, 2016, 3:50 p.m. UTC | #1 
Hello,

Thanks, this looks good, with one nit, see below.

On Wed, 10 Feb 2016 13:33:12 -0200, Carlos Santos wrote:

> diff --git a/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
> new file mode 100644
> index 0000000..237bc71
> --- /dev/null
> +++ b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
> @@ -0,0 +1,34 @@
> +From 0883fa19d59ece19eec30937c65fd10162ef57b0 Mon Sep 17 00:00:00 2001
> +From: Carlos Santos <casantos@datacom.ind.br>
> +Date: Wed, 10 Feb 2016 12:54:43 -0200
> +Subject: [PATCH] configure.ac: check if libatomic is needed
> +
> +In Buildroot, to simplify things, we've decided to simply require gcc 4.8
> +as soon as the architectures has at least one __atomic_*() built-in
> +variant that requires libatomic.
> +
> +Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
> +*could* technically build with gcc 4.7. This is probably not a big deal,
> +and we can live with requiring gcc 4.8 on PowerPC to build protobuf.
> +
> +Signed-off-by: Carlos Santos <casantos@datacom.ind.br>

The patch description should not mention Buildroot and not mention
Buildroot specific choices. It should be written as if you were going
to submit it upstream, i.e with a proper justification as to why
linking with libatomic may be needed.

And in fact, I'm even going to ask you to submit this patch upstream :-)

Thanks a lot!

Thomas
Carlos Santos Feb. 10, 2016, 6:42 p.m. UTC | #2 
[Thanks, Zimbra, for messing rearranging the messages in the inbox, so I answer them in the wrong order].

> From: "Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>
> To: "Carlos Santos" <casantos@datacom.ind.br>
> Cc: buildroot@buildroot.org, "henrique marks" <henrique.marks@datacom.ind.br>
> Sent: Wednesday, February 10, 2016 1:50:37 PM
> Subject: Re: [PATCH 1/1] protobuf: fix detection of __atomic_*() built-ins

> Hello,
> 
> Thanks, this looks good, with one nit, see below.
> 
> On Wed, 10 Feb 2016 13:33:12 -0200, Carlos Santos wrote:
> 
>> diff --git
>> a/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>> b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>> new file mode 100644
>> index 0000000..237bc71
>> --- /dev/null
>> +++ b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>> @@ -0,0 +1,34 @@
>> +From 0883fa19d59ece19eec30937c65fd10162ef57b0 Mon Sep 17 00:00:00 2001
>> +From: Carlos Santos <casantos@datacom.ind.br>
>> +Date: Wed, 10 Feb 2016 12:54:43 -0200
>> +Subject: [PATCH] configure.ac: check if libatomic is needed
>> +
>> +In Buildroot, to simplify things, we've decided to simply require gcc 4.8
>> +as soon as the architectures has at least one __atomic_*() built-in
>> +variant that requires libatomic.
>> +
>> +Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
>> +*could* technically build with gcc 4.7. This is probably not a big deal,
>> +and we can live with requiring gcc 4.8 on PowerPC to build protobuf.
>> +
>> +Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
> 
> The patch description should not mention Buildroot and not mention
> Buildroot specific choices. It should be written as if you were going
> to submit it upstream, i.e with a proper justification as to why
> linking with libatomic may be needed.

This patch only exists to appease Buildroot but, anyway, I can rewrite the comment.

> And in fact, I'm even going to ask you to submit this patch upstream :-)

They don't need this. Their detection of the atomic built-ins already works without additional help.

Carlos Santos (Casantos)
DATACOM, P&D
Arnout Vandecappelle Feb. 10, 2016, 8 p.m. UTC | #3 
On 10-02-16 16:33, Carlos Santos wrote:
[snip]
> +#
> +# On PowerPC, the __atomic_*() built-ins for 1-byte, 2-byte and 4-byte
> +# types are available built-in. However, the __atomic_*() built-ins for
> +# 8-byte types is implemented via libatomic, so only available since gcc
> +# 4.8.
> +#
> +# In Buildroot, to simplify things, we've decided to simply require gcc
> +# 4.8 as soon as the architectures has at least one __atomic_*() built-in
> +# variant that requires libatomic.
> +#
> +# Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
> +# *could* technically build with gcc 4.7. This is probably not a big deal,
> +# and we can live with requiring gcc 4.8 on PowerPC to build protobuf. 
> +#
>  # host-protobuf only builds on certain architectures
>  config BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
>  	bool
> -	default y if BR2_arm
> -	default y if BR2_i386
> -	default y if BR2_mipsel
> -	default y if BR2_x86_64

 Sorry for my confusion, but why do you remove these? It will still work with
gcc 4.7 on arm, i386, mipsel and x86_64 because it will use its custom atomic
implementation, no?


 Regards,
 Arnout

> +	default y if BR2_TOOLCHAIN_HAS_ATOMIC
>  	depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86"
[snip]
Arnout Vandecappelle Feb. 10, 2016, 8:06 p.m. UTC | #4 
On 10-02-16 19:42, Carlos Santos wrote:
> [Thanks, Zimbra, for messing rearranging the messages in the inbox, so I answer them in the wrong order].
> 
>> From: "Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>
>> To: "Carlos Santos" <casantos@datacom.ind.br>
>> Cc: buildroot@buildroot.org, "henrique marks" <henrique.marks@datacom.ind.br>
>> Sent: Wednesday, February 10, 2016 1:50:37 PM
>> Subject: Re: [PATCH 1/1] protobuf: fix detection of __atomic_*() built-ins
> 
>> Hello,
>>
>> Thanks, this looks good, with one nit, see below.
>>
>> On Wed, 10 Feb 2016 13:33:12 -0200, Carlos Santos wrote:
>>
>>> diff --git
>>> a/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>>> b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>>> new file mode 100644
>>> index 0000000..237bc71
>>> --- /dev/null
>>> +++ b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
>>> @@ -0,0 +1,34 @@
>>> +From 0883fa19d59ece19eec30937c65fd10162ef57b0 Mon Sep 17 00:00:00 2001
>>> +From: Carlos Santos <casantos@datacom.ind.br>
>>> +Date: Wed, 10 Feb 2016 12:54:43 -0200
>>> +Subject: [PATCH] configure.ac: check if libatomic is needed
>>> +
>>> +In Buildroot, to simplify things, we've decided to simply require gcc 4.8
>>> +as soon as the architectures has at least one __atomic_*() built-in
>>> +variant that requires libatomic.
>>> +
>>> +Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
>>> +*could* technically build with gcc 4.7. This is probably not a big deal,
>>> +and we can live with requiring gcc 4.8 on PowerPC to build protobuf.
>>> +
>>> +Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
>>
>> The patch description should not mention Buildroot and not mention
>> Buildroot specific choices. It should be written as if you were going
>> to submit it upstream, i.e with a proper justification as to why
>> linking with libatomic may be needed.
> 
> This patch only exists to appease Buildroot but, anyway, I can rewrite the comment.
> 
>> And in fact, I'm even going to ask you to submit this patch upstream :-)
> 
> They don't need this. Their detection of the atomic built-ins already works without additional help.

 Clearly it doesn't work, or this wouldn't be needed...

 Except if they specifically want to exclude any architecture for which they
don't have their custom atomics implementation.

 By the way, you check for atomic_4, which happens to be a special case on
microblaze: it doesn't need -latomic for atomic_4, but it does for the others.
So if they do use any other atomic operation, it would be better to check for
atomic_2 or atomic_1 (or better yet, all of them).

 Regards,
 Arnout
Carlos Santos Feb. 11, 2016, 2:56 p.m. UTC | #5 
> From: "Arnout Vandecappelle" <arnout@mind.be>
> To: "Carlos Santos" <casantos@datacom.ind.br>, buildroot@buildroot.org
> Cc: "thomas petazzoni" <thomas.petazzoni@free-electrons.com>
> Sent: Wednesday, February 10, 2016 6:00:16 PM
> Subject: Re: [Buildroot] [PATCH 1/1] protobuf: fix detection of __atomic_*() built-ins

> On 10-02-16 16:33, Carlos Santos wrote:
> [snip]
>> +#
>> +# On PowerPC, the __atomic_*() built-ins for 1-byte, 2-byte and 4-byte
>> +# types are available built-in. However, the __atomic_*() built-ins for
>> +# 8-byte types is implemented via libatomic, so only available since gcc
>> +# 4.8.
>> +#
>> +# In Buildroot, to simplify things, we've decided to simply require gcc
>> +# 4.8 as soon as the architectures has at least one __atomic_*() built-in
>> +# variant that requires libatomic.
>> +#
>> +# Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
>> +# *could* technically build with gcc 4.7. This is probably not a big deal,
>> +# and we can live with requiring gcc 4.8 on PowerPC to build protobuf.
>> +#
>>  # host-protobuf only builds on certain architectures
>>  config BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
>>  	bool
>> -	default y if BR2_arm
>> -	default y if BR2_i386
>> -	default y if BR2_mipsel
>> -	default y if BR2_x86_64
> 
> Sorry for my confusion, but why do you remove these? It will still work with
> gcc 4.7 on arm, i386, mipsel and x86_64 because it will use its custom atomic
> implementation, no?

Ok, I will restore the prevoius defaults, allowing protobuf to build with gcc < 4.8.

Carlos Santos (Casantos)
DATACOM, P&D
diff mbox

Patch

diff --git a/package/protobuf/0001-Fix-GOOGLE_PROTOBUF_ATOMICOPS_ERROR-syntax-error.patch b/package/protobuf/0001-Fix-GOOGLE_PROTOBUF_ATOMICOPS_ERROR-syntax-error.patch
new file mode 100644
index 0000000..a46e459
--- /dev/null
+++ b/package/protobuf/0001-Fix-GOOGLE_PROTOBUF_ATOMICOPS_ERROR-syntax-error.patch
@@ -0,0 +1,61 @@ 
+From 7ad8690c5d8a875881ba00c3551595a2676538ef Mon Sep 17 00:00:00 2001
+From: George Redivo <george.redivo@datacom.ind.br>
+Date: Mon, 6 Jul 2015 16:56:41 -0300
+Subject: [PATCH] Fix GOOGLE_PROTOBUF_ATOMICOPS_ERROR syntax error
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+It's not possible to define "#error" inside a define.
+It causes 'error: stray ‘#’ in program' compilation error.
+
+Now the define GOOGLE_PROTOBUF_ATOMICOPS_ERROR is the error message
+and it's used along the code together "#error".
+---
+ src/google/protobuf/stubs/atomicops.h | 10 +++++-----
+ 1 file changed, 5 insertions(+), 5 deletions(-)
+
+diff --git a/src/google/protobuf/stubs/atomicops.h b/src/google/protobuf/stubs/atomicops.h
+index cd20caa..5fa31b0 100644
+--- a/src/google/protobuf/stubs/atomicops.h
++++ b/src/google/protobuf/stubs/atomicops.h
+@@ -173,7 +173,7 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
+ 
+ // Include our platform specific implementation.
+ #define GOOGLE_PROTOBUF_ATOMICOPS_ERROR \
+-#error "Atomic operations are not supported on your platform"
++"Atomic operations are not supported on your platform"
+ 
+ // ThreadSanitizer, http://clang.llvm.org/docs/ThreadSanitizer.html.
+ #if defined(THREAD_SANITIZER)
+@@ -183,7 +183,7 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
+ #if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64)
+ #include <google/protobuf/stubs/atomicops_internals_x86_msvc.h>
+ #else
+-GOOGLE_PROTOBUF_ATOMICOPS_ERROR
++#error GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+ #endif
+ 
+ // Solaris
+@@ -218,15 +218,15 @@ GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+ #if __has_extension(c_atomic)
+ #include <google/protobuf/stubs/atomicops_internals_generic_gcc.h>
+ #else
+-GOOGLE_PROTOBUF_ATOMICOPS_ERROR
++#error GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+ #endif
+ #else
+-GOOGLE_PROTOBUF_ATOMICOPS_ERROR
++#error GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+ #endif
+ 
+ // Unknown.
+ #else
+-GOOGLE_PROTOBUF_ATOMICOPS_ERROR
++#error GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+ #endif
+ 
+ // On some platforms we need additional declarations to make AtomicWord
+-- 
+2.5.0
+
diff --git a/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
new file mode 100644
index 0000000..237bc71
--- /dev/null
+++ b/package/protobuf/0002-configure.ac-check-if-libatomic-is-needed.patch
@@ -0,0 +1,34 @@ 
+From 0883fa19d59ece19eec30937c65fd10162ef57b0 Mon Sep 17 00:00:00 2001
+From: Carlos Santos <casantos@datacom.ind.br>
+Date: Wed, 10 Feb 2016 12:54:43 -0200
+Subject: [PATCH] configure.ac: check if libatomic is needed
+
+In Buildroot, to simplify things, we've decided to simply require gcc 4.8
+as soon as the architectures has at least one __atomic_*() built-in
+variant that requires libatomic.
+
+Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
+*could* technically build with gcc 4.7. This is probably not a big deal,
+and we can live with requiring gcc 4.8 on PowerPC to build protobuf.
+
+Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
+---
+ configure.ac | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/configure.ac b/configure.ac
+index c07067c..88d4a0d 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -139,6 +139,8 @@ AM_CONDITIONAL([USE_EXTERNAL_PROTOC], [test "$with_protoc" != "no"])
+ ACX_PTHREAD
+ AC_CXX_STL_HASH
+ 
++AC_SEARCH_LIBS([__atomic_load_4], [atomic])
++
+ case "$target_os" in
+   mingw* | cygwin* | win*)
+     ;;
+-- 
+2.5.0
+
diff --git a/package/protobuf/Config.in b/package/protobuf/Config.in
index 3d4320b..f4f428a 100644
--- a/package/protobuf/Config.in
+++ b/package/protobuf/Config.in
@@ -1,12 +1,22 @@ 
 # See src/google/protobuf/stubs/platform_macros.h for supported archs.
-# PowerPC doesn't actually work.
+#
+# On PowerPC, the __atomic_*() built-ins for 1-byte, 2-byte and 4-byte
+# types are available built-in. However, the __atomic_*() built-ins for
+# 8-byte types is implemented via libatomic, so only available since gcc
+# 4.8.
+#
+# In Buildroot, to simplify things, we've decided to simply require gcc
+# 4.8 as soon as the architectures has at least one __atomic_*() built-in
+# variant that requires libatomic.
+#
+# Since protobuf most likely only uses the 1, 2 and 4-byte variants, it
+# *could* technically build with gcc 4.7. This is probably not a big deal,
+# and we can live with requiring gcc 4.8 on PowerPC to build protobuf. 
+#
 # host-protobuf only builds on certain architectures
 config BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
 	bool
-	default y if BR2_arm
-	default y if BR2_i386
-	default y if BR2_mipsel
-	default y if BR2_x86_64
+	default y if BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86"
 
 config BR2_PACKAGE_PROTOBUF