mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-12-27 08:55:39 +00:00
92 lines
2.8 KiB
Plaintext
92 lines
2.8 KiB
Plaintext
= Design Notes
|
|
|
|
== Problems:
|
|
|
|
Translating C to Go is harder than it looks.
|
|
|
|
Jan says: It's impossible in the general case to turn C char* into Go
|
|
[]byte. It's possible to do it probably often for concrete C code
|
|
cases - based also on author's C coding style. The first problem this
|
|
runs into is that Go does not guarantee that the backing array will
|
|
keep its address stable due to Go movable stacks. C expects the
|
|
opposite, a pointer never magically modifies itself, so some code will
|
|
fail.
|
|
|
|
INSERT CODE EXAMPLES ILLUSTRATING THE PROBLEM HERE
|
|
|
|
== How the parser works
|
|
|
|
There are no comment nodes in the C AST. Instead every cc.Token has a
|
|
Sep field: https://godoc.org/modernc.org/cc/v3#Token
|
|
|
|
It captures, when configured to do so, all white space preceding the
|
|
token, combined, including comments, if any. So we have all white
|
|
space/comments information for every token in the AST. A final white
|
|
space/comment, preceding EOF, is available as field TrailingSeperator
|
|
in the AST: https://godoc.org/modernc.org/cc/v3#AST.
|
|
|
|
To get the lexically first white space/comment for any node, use
|
|
tokenSeparator():
|
|
https://gitlab.com/cznic/ccgo/-/blob/6551e2544a758fdc265c8fac71fb2587fb3e1042/v3/go.go#L1476
|
|
|
|
The same with a default value is comment():
|
|
https://gitlab.com/cznic/ccgo/-/blob/6551e2544a758fdc265c8fac71fb2587fb3e1042/v3/go.go#L1467
|
|
|
|
== Looking forward
|
|
|
|
Eric says: In my visualization of how the translator would work, the
|
|
output of a ccgo translation of a module at any given time is a file
|
|
of pseudo-Go code in which some sections may be enclosed by a Unicode
|
|
bracketing character (presently using the guillemot quotes U+ab and
|
|
U+bb) meaning "this is not Go yet" that intentionally makes the Go
|
|
compiler barf. This expresses a color on the AST nodes.
|
|
|
|
So, for example, if I'm translating hello.c with a ruleset that does not
|
|
include print -> fmt.Printf, this:
|
|
|
|
---------------------------------------------------------
|
|
#include <stdio>
|
|
|
|
/* an example comment */
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
printf("Hello, World")
|
|
}
|
|
---------------------------------------------------------
|
|
|
|
becomes this without any explicit rules at all:
|
|
|
|
---------------------------------------------------------
|
|
«#include <stdio>»
|
|
|
|
/* an example comment */
|
|
|
|
func main
|
|
{
|
|
«printf(»"Hello, World"!\n"«)»
|
|
}
|
|
---------------------------------------------------------
|
|
|
|
Then, when the rule print -> fmt.Printf is added, it becomes
|
|
|
|
---------------------------------------------------------
|
|
import (
|
|
"fmt"
|
|
)
|
|
|
|
/* an example comment */
|
|
|
|
func main
|
|
{
|
|
fmt.Printf("Hello, World"!\n")
|
|
}
|
|
---------------------------------------------------------
|
|
|
|
because with that rule the AST node corresponding to the printf
|
|
call can be translated and colored "Go". This implies an import
|
|
of fmt. We observe that there are no longer C-colored spans
|
|
and drop the #includes.
|
|
|
|
// end
|