From 662e44632192d1eabb2e31c4eb72ebd97b7f5a8d Mon Sep 17 00:00:00 2001
From: "clemens.schmid@esrf.fr" <clemens.schmid@esrf.fr>
Date: Tue, 25 Aug 2026 10:39:18 +0200
Subject: [PATCH 1/3] add arch flag to scons build command

scons arch=native        lib     # local
scons arch=x86-64-v3     lib     # portable AVX2 deploy
scons                    lib     # default: no -march (unchanged behaviour)

or via

$ export OBJCRYST_ARCH=x86-64-v3
---
 SConstruct | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/SConstruct b/SConstruct
index a525990b..852f0bfd 100644
--- a/SConstruct
+++ b/SConstruct
@@ -75,6 +75,12 @@ vars.Add(EnumVariable(
 vars.Add(BoolVariable(
     'profile',
     'build with profiling information', False))
+vars.Add(
+    'arch',
+    'target CPU passed to -march in the \'fast\' build, e.g. \'native\' for local '
+    'builds or \'x86-64-v3\' for a portable AVX2 deployment. Empty means no -march. '
+    'Defaults to the OBJCRYST_ARCH environment variable if set.',
+    os.environ.get('OBJCRYST_ARCH', ''))
 vars.Update(env)
 
 # Use C++ compiler specified by the 'tool' option.
@@ -184,6 +190,8 @@ else:
     else:
         env.AppendUnique(CCFLAGS=['-fno-strict-aliasing'])
         fast_opts = ['-ffast-math']
+        if env.get('arch'):
+            fast_opts.append('-march=' + env['arch'])       
 
     if env['PLATFORM'] == 'darwin':
         # macOS bundle

From b4d9008463bd0dc46440c57e3ed10f54a6c24bf7 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 25 Aug 2026 08:41:10 +0000
Subject: [PATCH 2/3] [pre-commit.ci] auto fixes from pre-commit hooks

---
 SConstruct | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/SConstruct b/SConstruct
index 852f0bfd..fd66c232 100644
--- a/SConstruct
+++ b/SConstruct
@@ -191,7 +191,7 @@ else:
         env.AppendUnique(CCFLAGS=['-fno-strict-aliasing'])
         fast_opts = ['-ffast-math']
         if env.get('arch'):
-            fast_opts.append('-march=' + env['arch'])       
+            fast_opts.append('-march=' + env['arch'])
 
     if env['PLATFORM'] == 'darwin':
         # macOS bundle

From 3c32e5621fc52576931532b059023bef548049fd Mon Sep 17 00:00:00 2001
From: Clemens Schmid <clem.schmid@gmail.com>
Date: Tue, 25 Aug 2026 13:43:19 +0200
Subject: [PATCH 3/3] add news file

---
 news/compile_arch.rst | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 news/compile_arch.rst

diff --git a/news/compile_arch.rst b/news/compile_arch.rst
new file mode 100644
index 00000000..f1a594d2
--- /dev/null
+++ b/news/compile_arch.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* Add SCons ``arch`` option to set architecture during compilation. By default, no arch is specified.
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>