BUG, BLD: Generate the main dispatcher config header into the build dir

  The new path becomes `build/src.*/numpy/distutils/include/npy_cpu_dispatch_config.h`
  instead of `numpy/core/src/common/_cpu_dispatch.h`.

  The new path allows other projects to re-use the CPU dispatcher
  once we decide to expose the following headers:
    - `numpy/core/src/common/npy_cpu_dispatch.h`
    - `numpy/core/src/common/npy_cpu_features.h`

1 files changed, 16 insertions, 6 deletions

diff --git a/numpy/distutils/command/build_ext.py b/numpy/distutils/command/build_ext.py
index ca6f8bcd2..448f7941c 100644
--- a/numpy/distutils/command/build_ext.py
+++ b/numpy/distutils/command/build_ext.py
@@ -146,11 +146,16 @@ class build_ext (old_build_ext):
         self.compiler.show_customization()
 
         if not self.disable_optimization:
-            opt_cache_path = os.path.abspath(os.path.join(self.build_temp, 'ccompiler_opt_cache_ext.py'))
-            self.compiler_opt = new_ccompiler_opt(compiler=self.compiler,
-                                                  cpu_baseline=self.cpu_baseline,
-                                                  cpu_dispatch=self.cpu_dispatch,
-                                                  cache_path=opt_cache_path)
+            dispatch_hpath = os.path.join("numpy", "distutils", "include", "npy_cpu_dispatch_config.h")
+            dispatch_hpath = os.path.join(self.get_finalized_command("build_src").build_src, dispatch_hpath)
+            opt_cache_path = os.path.abspath(
+                os.path.join(self.build_temp, 'ccompiler_opt_cache_ext.py')
+            )
+            self.compiler_opt = new_ccompiler_opt(
+                compiler=self.compiler, dispatch_hpath=dispatch_hpath,
+                cpu_baseline=self.cpu_baseline, cpu_dispatch=self.cpu_dispatch,
+                cache_path=opt_cache_path
+            )
             if not self.compiler_opt.is_cached():
                 log.info("Detected changes on compiler optimizations, force rebuilding")
                 self.force = True
@@ -416,7 +421,12 @@ class build_ext (old_build_ext):
         copt_baseline_flags = []
         copt_macros = []
         if not self.disable_optimization:
-            copt_build_src = None if self.inplace else self.get_finalized_command("build_src").build_src
+            bsrc_dir = self.get_finalized_command("build_src").build_src
+            dispatch_hpath = os.path.join("numpy", "distutils", "include")
+            dispatch_hpath = os.path.join(bsrc_dir, dispatch_hpath)
+            include_dirs.append(dispatch_hpath)
+
+            copt_build_src = None if self.inplace else bsrc_dir
             copt_c_sources = [
                 c_sources.pop(c_sources.index(src))
                 for src in c_sources[:] if src.endswith(".dispatch.c")