Re: How to insert external global variable declarations and pointer assignment statements through GCC plugin GIMPLE pass

[Ian Lance Taylor <iant@google.com>]

"Abhijit Nandy" <abhijit.nandy@gmail.com> writes:

> My C input file is testcode.c and after I compile with the plugin
> enabled as :
>
> gcc -fplugin=./test_plugin.so -Wall -fdump-tree-gimple -fdump-tree-all
> testcode.c molen_htx.c -o testcode
>
> The molen_htx.c has the molen_elfset()
>
> I get the following linker error :
>
> root@slax:/mnt/f/Thesis/gcc-pluginelf# make testcode
> cc -I/usr/lib/gcc/i486-slackware-linux/4.5.2/plugin/include -fPIC
> -Wall   -c 
> -o test_plugin.o test_plugin.c
> gcc -shared test_plugin.o -o test_plugin.so
> gcc -fplugin=./test_plugin.so -Wall -fdump-tree-gimple -fdump-tree-all
> testcode.c molen_htx.c -o testcode
> plugin init test_plugin
> testcode.c: In function 'main':
> testcode.c:26:7: warning: unused variable 'q'
> plugin init test_plugin
> /tmp/ccLUccsU.o: In function `main':
> testcode.c:(.text+0x82): undefined reference to `_binary_ccu_start'
> <---------------
> collect2: ld returned 1 exit status
> make: *** [testcode] Error 1
>
>
> A dump file called testcode.c.220t.replace is produced which does not
> show the global declaration(if it is being inserted at all)
>
> But the undefined reference implies that the global extern declaration
> was not inserted.

A global extern declaration is not a definition.  The variable needs to
be defined somewhere.

If your .c file has "extern char _binary_ccu_start;" you still need to
have some .c file which has "char _binary_ccu_start;", right?

Ian