v_random is a variable
random is a signal
The following libraries are added
I get the error with following libraries and packages.
# ** Error: ./(vcom-1078) Identifier "signed" is not directly visible.
If I disable use IEEE.std_logic_arith.all; then I get the following warning.
# ** Warning: NUMERIC_STD.TO_INTEGER: metavalue detected, returning 0
# Time: 2480 ns Iteration: 0
How critical is this warning ?
That depends; if it were always critical, it would be an error.
Discussion on StackOverflow and EDA Board indicate it happens when a vector that has a value of X or Z is cast to an integer, and that if you are getting this after resetting your design (when variables should be re-initialized) it can be an indicator of a serious problem.
In the ModelSim User's Manual, under "Miscellaneous Messages," there is this chunk:
Metavalue detected warning
Warning: NUMERIC_STD.">": metavalue detected, returning FALSE
• Description — This warning is an assertion being issued by the IEEE numeric_std
package. It indicates that there is an 'X' in the comparison.
• Suggested action — The message does not indicate which comparison is reporting the
problem since the assertion is coming from a standard package. To track the problem,
note the time the warning occurs, restart the simulation, and run to one time unit before
the noted time. At this point, start stepping the simulator until the warning appears. The
location of the blue arrow in a Source window will be pointing at the line following the
line with the comparison.
These messages can be turned off by setting the NumericStdNoWarnings variable to 1
from the command line or in the modelsim.ini file.
So, is it critical? Only you (or someone who can help you poke at the design) can say for sure.