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Subject: Re: [OMPI devel] usage of mca variables in orte-restart
From: Adrian Reber (adrian_at_[hidden])
Date: 2014-03-17 09:50:02


On Fri, Mar 14, 2014 at 10:18:06PM +0000, Hjelm, Nathan T wrote:
> The preferred way is to use mca_base_var_find and then call mca_base_var_[set|get]_value. For performance sake we only look at the environment when the variable is registered.

I believe I found a bug in mca_base_var_set_value using bool variables:

#0 0x00007f6e0d8fb800 in mca_base_var_enum_bool_sfv (self=0x7f6e0dbabc20 <mca_base_var_enum_bool>, value=0,
    string_value=0x0) at ../../../../opal/mca/base/mca_base_var_enum.c:82
#1 0x00007f6e0d8f45d6 in mca_base_var_set_value (vari=120, value=0x4031e6, size=0, source=MCA_BASE_VAR_SOURCE_DEFAULT,
    source_file=0x0) at ../../../../opal/mca/base/mca_base_var.c:636
#2 0x0000000000401e44 in main (argc=7, argv=0x7fffa72a0a78) at ../../../../opal/tools/opal-restart/opal-restart.c:223

I am using set_value like this:

bool test=false;
mca_base_var_set_value(idx, &test, 0, MCA_BASE_VAR_SOURCE_DEFAULT, NULL);

As the size is ignored I am just setting it to '0'.

mca_base_var_set_value() does

ret = var->mbv_enumerator->string_from_value(var->mbv_enumerator,((int *) value)[0], NULL);

which calls mca_base_var_enum_bool_sfv() with the last parameter set to NULL:

static int mca_base_var_enum_bool_sfv (mca_base_var_enum_t *self, const int value,
                                       const char **string_value)
{
    *string_value = value ? "true" : "false";

    return OPAL_SUCCESS;
}

and here it tries to access the last parameter (string_value) which has
been set to NULL. As I cannot find any usage of mca_base_var_set_value()
with bool variables this code path has probably not been used until now.

                Adrian