3

UPDATE I know now that parser.h should be generated by the make system from parser.y. The Android.mk file even has an entry like this:

edify_src_files := \ lexer.l \ parser.y \ expr.c

But I still can't seem to get the executable out of it. (Yes, excecutable, not shared library)

I'm trying to compile Android Wifi Tether (http://code.google.com/p/android-wifi-tether/) by myself and while trying to compile some C code related to the JNI part of the project there is some weird use of lex/yacc.

I've never dealt with parsers before so I'm really with my hands tight here. While using the latest ndk-build script (ndk-r5b) and after sorting some other problems I find myself looking for a parser.h header file. I tryied to compile without including it and the function calls that had undefined references were:

  • yy_scan_string
  • yy_scan_bytes
  • yyparse

So I clearly need to find the path to this parser.h file where these functions should be declared. Problem is that by issuing a locate command I get a huge list of files with the same name in my system, but it seems like none of them is the one I'm looking for.

Can someone give me a light here? maybe I need to install a developer package?

Thanks!

Nelson

Bilthon
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  • You probably just need to install flex and bison, so the build script can use them to generate parser.h and various other things that are needed. – Chris Dodd Mar 24 '11 at 00:35
  • I have both flex and bison installed in my system. I was also able to generate all the .c and .h files by the process described by Beco below. But it seems that the android build mechanism is somewhat different. Looking at what is written in the Makefile.mk file I get the impression that the arm crosscompiler should be able to process the .y and .l files and generate the .c and .h. – Bilthon Mar 24 '11 at 04:24

1 Answers1

1

You can find the definition of:

YY_BUFFER_STATE yy_scan_string (yyconst char *yy_str  );
YY_BUFFER_STATE yy_scan_bytes (yyconst char *bytes,int len  );

in a ".c" automatically generated file by the lexical scanner called "lex" (or flex). So, if you do not intend to write them by yourself, you need a mylex.l to apply to lex, and it will usually create a file called lex.yy.c.

This file can be used together with a syntactical parser ".y" that describes your grammar. In the other ".c" generated automatically by this other tool called "bison" or "yacc", you will find:

int yyparse (void *YYPARSE_PARAM);

You can instruct yacc to create 2 files: parser.c and parser.h, both coming from another file you need to write, lets say, mygrammar.y.

So, briefly, you need to write:

  • mylex.l
  • mygrammar.y

And then run:

  • flex mylex.l ==> gives you lex.yy.c
  • bison --defines=parser.h --output=parser.c mygrammar.y ==> gives you parser.h parser.c

You can try to find in the project files like mylex.l and mygrammar.y (probably with better names). If the project don't give you the sources (.l and .y) neither the scanner/parser (lex.yy.c and parse.c/parser.h), you need to write them.

I hope this helps you.

Beco

DrBeco
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  • Really good answer Beco!! I found out some of the things that you say the hard way since I first posted the question, but you saying it just reinforces that what I did was in the right path. I still can't come up with a binary though and the reason might be related with the strange build process of the android NDK. – Bilthon Mar 24 '11 at 04:16
  • Thanks. I'm glad I could be of some help. Hope you get your way through it. ;) – DrBeco Mar 24 '11 at 04:23