Day: August 11, 2017

Include “stdio.h” before Readline library header files

I install Readline library and write a simple program to play with it:

#include <readline/readline.h>
#include <readline/history.h>

int main(void)
{
    char *line_read = readline (">>  ");
    if (line_read && *line_read)
    {
        add_history (line_read);
    }
    ......
}

Build it will generate following errors:

In file included from /usr/include/readline/readline.h:35:0,
                 from readline.c:3:
/usr/include/readline/rltypedefs.h:71:28: error: unknown type name 'FILE'
 typedef int rl_getc_func_t PARAMS((FILE *));
                            ^
/usr/include/readline/readline.h:429:20: error: unknown type name 'FILE'
 extern int rl_getc PARAMS((FILE *));
                    ^
In file included from readline.c:3:0:
/usr/include/readline/readline.h:558:8: error: unknown type name 'FILE'
 extern FILE *rl_instream;
        ^~~~
/usr/include/readline/readline.h:559:8: error: unknown type name 'FILE'
 extern FILE *rl_outstream;
        ^~~~
/usr/include/readline/readline.h:588:8: error: unknown type name 'rl_getc_func_t'
 extern rl_getc_func_t *rl_getc_function;
        ^~~~~~~~~~~~~~
/usr/include/readline/readline.h:917:3: error: unknown type name 'FILE'
   FILE *inf;
   ^~~~
/usr/include/readline/readline.h:918:3: error: unknown type name 'FILE'
   FILE *outf;

The solution is including <stdio.h> before Readline library’s header files:

#include <stdio.h>
#include <readline/readline.h>
#include <readline/history.h>
......

Use Ctxt::isCorrect() to check Ctxt valid in using HElib

During using HElib, if the calculation made Ctxt‘s noise too big, it will cause Ctxt can’t be decrypted successfully, and the decrypted result is messy like this:

333317397173303 1016371194582039 217550837977960
737191953777559 1103851234911944 454685807668230
625213263895453 743713807221034 1036409711005678
447878070619549 603715795412661 948856958008786
......

You can leverage Ctxt::isCorrect() method to check whether Ctxt is still valid or not:

std::cout << "Ctxt is valid: " << c.isCorrect() << '\n';

Reference:
Maybe the bug in EncryptedArray’s shift function.

The subtleties of writing DTrace scripts

(1) Assume you write your DTrace script on Windows and run it on Unix. Because Windows uses \r\n as EOL while Unix uses \n, if you execute it directly, following complain will occur:

: No such file or directory

The solution is to apply dos2unix to convert file format before playing it.

(2) The shebang line of script only accepts 1 argument, and -s option must be the last. For example:

#!/usr/sbin/dtrace -sq

Will generate following error:

dtrace: failed to open q: No such file or directory

While “#!/usr/sbin/dtrace -qs” will be OK. To make additional options take effect, please use #pragma directive:

#pragma D option ...

Reference:
Does DTrace script only support “#pragma D option ..”, not “-x option”?.