Passing an sformat-formatted string to a DPI function

Hi all:

Verilator does not seem to have a $system() task, and I wish to run a shell command at the beginning of the simulation, but only after my DPI module has created a listening socket. This is what I've written so far:

import "DPI-C" function int uart_dpi_run_shell_command ( input string shell_cmd_to_run,
                                                         output int command_exit_code );

That works fine, but now I wish to build the shell_cmd_to_run string with Verilog parameters. I've tried this:

$sformat( shell_cmd,
          "gnome-terminal --command \"sh -c 'socat -,raw TCP4:localhost:%d'\" &",
          `UART_DPI_TELNET_PORT );

If I define shell_cmd like this:

reg [127*8:0] shell_cmd;

Then $sformat() fills the string with leading zeroes, and the DPI module things the string is empty.

On the other hand, if I define shell_cmd like this:

string shell_cmd;

Then I get this compilation error:

error: cannot convert ‘std::string’ to ‘void*’ for argument ‘2’ to ‘void VL_SFORMAT_X(int, void*, const char*, ...)’

I guess "input string" in the DPI function declaration translates to "const char*" in the generated .h file, but the "string shell_cmd" declaration creates an std::string. Somewhere is a call to std::string::c_str() probably missing.

Can someone help me here?

Thanks in advance, R. Diez

Replies (6)

RE: Passing an sformat-formatted string to a DPI function - Added by Wilson Snyder 6 months ago

Alas you need you function to take a verilog array and strip the leading zeros.

Alternatively, perhaps you could make a patch to support system? You can copy fopen code more or less.

RE: Passing an sformat-formatted string to a DPI function - Added by Wilson Snyder 6 months ago

Btw, either way feel free to file an unsupported bug to support $system.

RE: Passing an sformat-formatted string to a DPI function - Added by Wilson Snyder 6 months ago

Great work making your example code. I've also added support for the next release.

RE: Passing an sformat-formatted string to a DPI function - Added by vsevolod predtechensky 5 months ago

as a temporary solution, I found the following to work when passing systemverilog strings to dpi functions:

in a verilog code do the following gasket: ... s1 = "abcdefgh"; //whatever text assigned to your string directly or with $sformat ... $sformat(conv_array,"%s",s1); //wrapper that makes types compatible

your_DPI_call(conv_array);

notice that in DPI import an argument should be defined as input string

this is a temporary solution until Wilson releases a version that casts the strings correctly into C.

On a side, support for systemverilog string functions would be very beneficial and should not be too difficult to do - making wrappers for each function is a pain

RE: Passing an sformat-formatted string to a DPI function - Added by Wilson Snyder 5 months ago

BTW if you need $system it was put in 3.830.

RE: Passing an sformat-formatted string to a DPI function - Added by vsevolod predtechensky 5 months ago

however I still cannot make passing the verilog-defined strings to DPI functions correctly. dpi "input string" requires to be defined as reg[ ] and string should be passed through $sformat(reg, "%s", string) to work. I cannot make output string work. According to the above - regress_test(input string i, output string o) may not work correctly, it mistakenly returns "ok". I'm still playing with the code to make sure that its a bug and not a mistake in my setup.

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