MCA_BASE_VAR_SCOPE_READONLY and MCA_BASE_VAR_SCOPE_CONSTANT still set a variable to "writable"

[jsquyres]

Per #4992, if I set an MCA param to MCA_BASE_VAR_SCOPE_CONSTANT, it still shows up as "writable" in ompi_info output:

$ ompi_info --param pmix pmix3x --parsable --level 9 | grep library_version
mca:pmix:pmix3x:param:pmix_pmix3x_library_version:value:PMIx library version 3.0.0 (embedded in Open MPI)
mca:pmix:pmix3x:param:pmix_pmix3x_library_version:source:default
mca:pmix:pmix3x:param:pmix_pmix3x_library_version:status:writeable

I note that the same thing happens if I change the code to use MCA_BASE_VAR_SCOPE_READONLY, too.

Here's the code in question -- am I doing something wrong?

    asprintf(&pmix_library_version,
             "PMIx library version %s (embedded in Open MPI)", PMIx_Get_version());
    (void) mca_base_component_var_register(component, "library_version",
                                           "Version of the underlying PMIx library",
                                           MCA_BASE_VAR_TYPE_STRING,
                                           NULL, 0, 0,
                                           OPAL_INFO_LVL_4,
                                           MCA_BASE_VAR_SCOPE_READONLY,
                                           &pmix_library_version);

I see the same thing on other READONLY variables, too, such as mca_base_param_files (registered as READONLY here)

$ ompi_info --all --level 9 --parsable | grep base_param_files
mca:mca:base:param:mca_param_files:synonym_of:name:mca_base_param_files
mca:mca:base:param:mca_base_param_files:value:"/home/jsquyres/.openmpi/mca-params.conf:/home/jsquyres/bogus/etc/openmpi-mca-params.conf"
mca:mca:base:param:mca_base_param_files:source:default
mca:mca:base:param:mca_base_param_files:status:writeable
...

[jsquyres]

@hjelmn is this the correct fix? If so, I'll make a PR.

diff --git a/opal/mca/base/mca_base_var.c b/opal/mca/base/mca_base_var.c
index 9b07a9664e..ffa73de54b 100644
--- a/opal/mca/base/mca_base_var.c
+++ b/opal/mca/base/mca_base_var.c
@@ -2146,7 +2146,9 @@ int mca_base_var_dump(int vari, char ***out, mca_base_var_dump
         asprintf(out[0] + line++, "%ssource:%s", tmp, source_string);
 
         /* Output whether it's read only or writable */
-        asprintf(out[0] + line++, "%sstatus:%s", tmp, VAR_IS_DEFAULT_ONLY(var[0]) ?
+        asprintf(out[0] + line++, "%sstatus:%s", tmp,
+                 (VAR_IS_DEFAULT_ONLY(var[0]) || !VAR_IS_SETTABLE(var[0])) ?
+                 "read-only" : "writeable");
 
         /* Output the info level of this parametere */
         asprintf(out[0] + line++, "%slevel:%d", tmp, var->mbv_info_lvl + 1);

[hjelmn]

@jsquyres That will work but I think we should also make sure to unset the settable flag on register.

[jsquyres]

@hjelmn looks like we already make sure to unset SETTABLE (see line 1394):

ompi/opal/mca/base/mca_base_var.c

Lines 1385 to 1395 in 3f598e9

	/* Read-only and constant variables can't be settable */
	if (scope < MCA_BASE_VAR_SCOPE_LOCAL || (flags & MCA_BASE_VAR_FLAG_DEFAULT_ONLY)) {
	if ((flags & MCA_BASE_VAR_FLAG_DEFAULT_ONLY) && (flags & MCA_BASE_VAR_FLAG_SETTABLE)) {
	opal_show_help("help-mca-var.txt", "invalid-flag-combination",
	true, "MCA_BASE_VAR_FLAG_DEFAULT_ONLY", "MCA_BASE_VAR_FLAG_SETTABLE");
	return OPAL_ERROR;
	}
	/* Should we print a warning for other cases? */
	flags &= ~MCA_BASE_VAR_FLAG_SETTABLE;
	}

So I think we don't need VAR_IS_DEFAULT_ONLY(var[0]) in the test clause at all.