Re: [Buildroot] [PATCH v2, 2/2] package/attr: affected by gcc bug 101766

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

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Hello Fabrice,

On Tue, 16 Jan 2024 07:58:31 +0100
Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:

> attr is affected by gcc bug 101766 since version 1.5.2 and
> https://git.savannah.nongnu.org/cgit/attr.git/commit/?id=11b9069098b4d4c23efb06c9457a085b784354d4
> resulting in the following build failure on microblaze since commit
> b31b91296e7f985b909f104f06a098adddef1fea:
> 
> libattr/syscalls.c:133:10: error: symver is only supported on ELF platforms
>   133 | # pragma GCC visibility pop
>       |          ^~~
> 
> So let's disable package attr and packages depending on it.
> 
> Fixes:
>  - http://autobuild.buildroot.org/results/29c76e02becedf922bd7dc0533338c078bf77d2a
> 
> Reviewed-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

I don't like this very much. It's annoying to propagate this dependency
to all reverse dependencies of attr, and make it unavailable on
Microblaze for this silly reason. So I came up with the attached patch
for attr, which rather detects if __attribute__(__symver__) works or
not, and fall backs to another mechanism if not (this fallback already
exists in the attr code).

Could you have a look at my proposal, and if it suits you, submit it
upstream and as a patch to Buildroot ? :-)

(Yeah, I know I'm pushing some of the work for you, my goal is to be
able to continue review/merge other patches)

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com

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From 1be7c2251040f1152de9ceb5263e6e96fa5c3d75 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Date: Tue, 6 Feb 2024 15:33:15 +0100
Subject: [PATCH] configure.ac: add detection of symver gcc attribute

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 configure.ac       | 15 +++++++++++++++
 libattr/syscalls.c |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 7e362e9..98477b5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -57,6 +57,21 @@ AS_CASE([$host_os],
 	[linux*], [os_linux=yes])
 AM_CONDITIONAL([OS_LINUX], [test "x$os_linux" = "xyes"])
 
+AC_CACHE_CHECK(whether __attribute__((__symver__())) is supported,
+	gcc_cv_symver_attribute,
+	[cat > conftest.c <<EOF
+void foo (void) {}
+__typeof(foo) foo __attribute__ ((__symver__("foo@foo")));
+EOF
+	gcc_cv_symver_attribute=no
+	if ${CC-cc} -Werror -S conftest.c -o conftest.s >/dev/null 2>&1; then \
+	    gcc_cv_symver_attribute=yes
+	fi
+	rm -f conftest.[cs]
+])
+AS_IF([test $gcc_cv_symver_attribute = yes],
+      [AC_DEFINE(HAVE_SYMVER_ATTRIBUTE, [], [GCC supports symver attribute])])
+
 AC_CONFIG_COMMANDS([include/attr],
 	[dnl
 	rm -rf include/attr
diff --git a/libattr/syscalls.c b/libattr/syscalls.c
index 907560a..caa70bc 100644
--- a/libattr/syscalls.c
+++ b/libattr/syscalls.c
@@ -32,7 +32,7 @@
  * fall back to traditional .symver asm directive otherwise.
  */
 #ifdef __has_attribute
-# if __has_attribute(__symver__)
+# if defined(HAVE_SYMVER_ATTRIBUTE)
 #  define SYMVER(cn, vn) __typeof(cn) cn __attribute__((__symver__(vn)))
 # elif __has_attribute(__no_reorder__)
    /*
-- 
2.43.0


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