Add rtems_get_build_hash()

[Sebastian Huber]

Add a function to report a hash value of the build environment in the test suite results.

/* Generated from spec:/rtems/config/if/get-build-hash */

/**
 * @ingroup RTEMSAPIConfig
 *
 * @brief Gets the RTEMS build hash.
 *
 * The build hash is calculated from all key-value pairs of the build
 * environment.  Local file system paths in the values do not contribute to the
 * hash value.
 *
 * @return Returns the pointer to the RTEMS build hash.
 *
 * @par Notes
 * The build hash can be used to distinguish test suite results obtained from
 * different build environments.
 *
 * @par Constraints
 * @parblock
 * The following constraints apply to this directive:
 *
 * * The directive may be called from within any runtime context.
 *
 * * The directive will not cause the calling task to be preempted.
 * @endparblock
 */
const char *rtems_get_build_hash( void );

[Chris Johns]

Is there a list that defines all key-value pairs in the build environment?

[Sebastian Huber]

Yes, you can iterate over conf.env:

wscript

@@ -1359 +1359 @@
     return value
 
 
+def _generate_build_hash(conf):
+    import hashlib
+    import base64
+
+    build_hash = ""
+    for key in sorted(conf.env):
+        build_hash = build_hash + key + str(conf.env[key])
+    for discard in [
+        conf.env.PREFIX,
+        conf.bldnode.make_node(conf.env.VARIANT).abspath(),
+        conf.path.abspath(),
+    ]:
+        build_hash = build_hash.replace(discard, "")
+    state = hashlib.sha256()
+    state.update(build_hash.encode("utf-8"))
+    conf.define("RTEMS_BUILD_HASH", base64.urlsafe_b64encode(state.digest()))
+    conf.write_config_header(
+        conf.env.VARIANT + "/cpukit/include/rtems/build-hash.h"
+    )
+
+
 def configure_variant(conf, cp, bsp_map, path_list, top_group, variant):
     conf.msg("Configure board support package (BSP)", variant, color="YELLOW")
 
@@ -1391 +1412 @@
         conf.fatal("No such base BSP: '{}'".format(variant))
     bsp_item.configure(conf, cic)
 
-    options = set([o[0].upper() for o in cp.items(variant)])
+    options = set(o[0].upper() for o in cp.items(variant))
     for o in options.difference(cic.options):
         conf.msg("Unknown configuration option", o.upper(), color="RED")
+    _generate_build_hash(conf)
 
 
 def check_forbidden_options(ctx, opts):

An alternative would be to explicitly add (or remove) build options.

[Chris Johns]

This captures a user's environment variables?

[Sebastian Huber]

There are always means to sabotage something. We don't recommend the use of environment variables and a waf configure warns about them. I will add a note that environment variables are not recommended and not used for the build hash.

[Sebastian Huber]

As discussed on the mailing list I tried the following approach. Iterate over all start files and libraries generated by the build and then create a hash of all executable sections. Then we recompile one object with a command line define with the build hash and replace this object in librtemscpu.a. Unfortunately, this exceeds my waf skills at the moment. I think it is feasible, but you really have to know how to adjust the waf tasks through meta programming.

[Sebastian Huber]

The rtems_get_build_hash() was dropped in favour of #4269.