Hello,
I have problems with emcc and node.ja when I test
a small interactive program:
---------- begin test program tst261.c ----------
#include <stdio.h>
int main(int argc, char *argv[])
{
char buf[100];
printf("Your input? ");
fflush(stdout);
while (fgets(buf, sizeof(buf), stdin) != NULL &&
buf[0] != '!') {
printf("You typed: %s", buf);
printf("Your input (Use ! to terminate)? ");
fflush(stdout);
}
return 0;
}
---------- end test program tst261.c ----------
When I use gcc and run the program afterwards it looks like follows:
myPrompt> gcc tst261.c -o tst261
myPrompt> ./tst261
Your input? test
You typed: test
Your input (Use ! to terminate)? another test
You typed: another test
Your input (Use ! to terminate)? !
myPrompt>
As you can see input and output can alternate.
With emcc and node.js it looks like follows:
myPrompt> emcc tst261.c -o tst261.js
myPrompt> node tst261.js
test
another test
!
<<< Here I typed cntl-d >>>
Your input? You typed: test
Your input (Use ! to terminate)? You typed: another test
stdio streams had content in them that was not flushed. you should set
EXIT_RUNTIME to 1 (see the FAQ), or make sure to emit a newline when you
printf etc.
myPrompt>
As you can see: After the start of the program all the
input must be typed in followed by cntl-d at the beginnig of a line.
Afterwards the program processes all given input in one batch.
Interestingly it is also possible to press cntl-d several times:
myPrompt> node tst261.js
test
<<< Here I typed cntl-d >>>
Your input? You typed: test
another test
<<< Here I typed cntl-d >>>
Your input (Use ! to terminate)? You typed: another test
!
<<< Here I typed cntl-d >>>
stdio streams had content in them that was not flushed. you should set
EXIT_RUNTIME to 1 (see the FAQ), or make sure to emit a newline when you
printf etc.
myPrompt>
I know that Javascript is single threaded, uses an event loop
and works with asynchronous I/O. But I think that it should be
possible to base a synchonous I/O on an asynchronous one.
All JavaScript "solutions" I found in the internet suggest, that
the program must register some callback (or use a Promise) an then
needs to terminate. Afterwards the event loop would call the callback
respecively Promise. In any such case the program is terminated
and executes in a callback function.
In the days when Pascal and other programming languages experimented
with cooperative multitasking it was always possible to write
such a simple interactive program like above. The sychronous
input function entered the event loop (where other events would be
handled just like the Javascript event loop does) and it came back,
when a keyboard input had been typed in.
I really cannot believe that it is not possible to compile such
a simple interactive program with emcc.
I have just started to compile my project (Seed7) with emcc.
Several things already work good, but interactive things do not.
I also need a synchronous solution to read single keypresses
without echo and a function to detect if a key has been pressed.
First I target node.js, but later the browsers are also a target.
Many thanks in advance for your help.
Regards,
Thomas Mertes
--
Seed7 Homepage: http://seed7.sourceforge.net
Seed7 - The extensible programming language: User defined statements
and operators, abstract data types, templates without special
syntax, OO with interfaces and multiple dispatch, statically typed,
interpreted or compiled, portable, runs under linux/unix/windows.
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