Unable to resolve compilation error in c file, provided with the lex/yacc book by John Levine.

ajiten · 01-22-2024, 05:28 AM

Quote:

Originally Posted by ntubski

In this case it is lib<something>.a, see https://cygwin.com/cygwin/packages/x...flex-2.6.4-0.1:

Also https://gcc.gnu.org/onlinedocs/gcc-1...ndex-Libraries:

Sorry, but if possible to see directly on cygwin, the details about: -lfl option for cc, which I hope is linker for flex.
I derived this (i.e., -lfl option for cc being for the linker) conclusion, as the response by @Nevem_Teve seems to point that the need for '-ll' (which I interpret as '-lfl' for flex) option for cc is obviated, if the yywrap() is specified in the lex file.

ajiten · 01-22-2024, 06:19 AM

Quote:

Originally Posted by NevemTeve

Off; no private messages, please
On: kindly read my previous posts: `-ll` is to be dropped; add this line into your program;

Code:

int yywrap(void) { return 1; }

PS: basic usage of the C-compiler should have been learnt already, but nonetheless here is a quickstart document: https://www3.ntu.edu.sg/home/ehchua/.../gcc_make.html

Please tell why the -lfl option, for cc in cygwin; is not needed, when add the stated yywrap(void) function, to the program.

Seems the -lfl option is for linker. If so, what role does it serve?

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Want to add that have come across just now, that states something similar (as shown in the attachment).

But, want to delve more into details, than by the one-liner stated there (i.e., 'The -lfl option to gcc tells the linker to link the flex runtime library into the executable.'), i.e. to see how the linker operates.

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2. Want to add to my last line above, that am not helped by the details offered here (also, shown in the attachment) or 'even' here, but need some practical exercises that really take to that level. Some source (book, site) would be needed, unless something is offered 'directly' by your kind side.

NevemTeve · 01-22-2024, 08:15 AM

Option `-ll` means: 'find and use libl.a (or libl.so, whichever comes first)', option `-lfl` means 'find and use libfl.a (or libfl.so)'.

`libl.a` belongs to the original `lex`, while `libfl.a` belongs to the replacement product `flex`.

Now the common part in these two is that you need neither of them.

ajiten · 01-22-2024, 11:23 PM

Quote:

Originally Posted by NevemTeve

Option `-ll` means: 'find and use libl.a (or libl.so, whichever comes first)', option `-lfl` means 'find and use libfl.a (or libfl.so)'.

`libl.a` belongs to the original `lex`, while `libfl.a` belongs to the replacement product `flex`.

Now the common part in these two is that you need neither of them.

Please tell if the lack of need of either of them, is due to including the yywrap() (and possibly other functions, though unneeded here). If yes, then please refer to some sources.

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Also, request how to get help on cc (gcc) options as '-lfl' on cygwin terminal, as the below attachment shows that couldn't get it.

NevemTeve · 01-23-2024, 01:03 AM

You have been given many documentation about gcc and ld, kindly read them. Also you can use command `man gcc`

`yywrap` is one of the functions you have to implement to get your lexical parser work. Resolving `yywrap` from an external library is a bad idea, even if it might occasionally work.

Off: if you wish to use Linux(ish subsystem) within Windows, use WSL1 with Ubuntu.

Off: `su`, `sudo`, `run` and other commands you tried in your Cygwin screenshot are completely off-topic.