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Full Discussion: What is the proper way to combine C++ files (with g++) to avoid link (ld) errors?
Top Forums Programming What is the proper way to combine C++ files (with g++) to avoid link (ld) errors? Post 302171728 by johnqsmith on Friday 29th of February 2008 09:30:51 AM
Old 02-29-2008
What is the proper way to combine C++ files (with g++) to avoid link (ld) errors?
Problem background:
gcc v 4.1
2 .cpp files, 2 .h files

Files:
main.cpp
a.cpp
a.h
b.h

Organization:
main.cpp includes a.h (because it calls a.cpp code)
a.cpp includes a.h
a.h includes b.h (because a class in a.h uses a b.h class)
There is no inheritance between a.h or b.h or any of the classes.

The problem is that when I try to compile the files like
g++ main.cpp a.cpp
I get an bunch of linker errors like "duplicate symbol X found..." which are for symbols from b.h

Normally I would think this is due to there not being #ifndef or #pragma once guards, but there are "#pragma once" things at the top of all the .h files. To me it seems like what is happening is that gcc is generating main.o separately from a.o and then then ld is called it sees duplication of symbols and it errors out. What is the correct way to tell g++ to compile them both while looking at them both?

I would think it would be something like --combine, but the man page and testing show that's only valid for C files.
I have also tried -shared which makes ld not complain but which says it's for making a shared library, so it doesn't seem correct for building an executable. Will using -shared lead to any strange behavior down the road (I need to know now since the application itself isn't in a state that I can test it, and I don't want to end up finding out it was the -shared flag's fault)
I have also tried -fwhole-program, which again works, but the man page says it's for optimization, so that also doesn't seem correct. Same question with regards to possible weird behavior down the road.

Thanks much for any help.

John
 

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LEARN ABOUT CENTOS

lupdate

lupdate(1)						      General Commands Manual							lupdate(1)

NAME

       lupdate - update Qt Linguist translation files

SYNOPSIS

       lupdate [ options ] project-file
       lupdate [ options ] source-files -ts ts-files

DESCRIPTION

       This  page  documents  the Qt Linguist Update tool for the Qt GUI toolkit.  Lupdate reads a qmake/tmake project file (.pro file), finds the
       translatable strings in the specified source, header and interface files, and updates the translation files (.ts files)	specified  in  it.
       The translation files are given to the translator who uses Qt Linguist to read the files and insert the translations.

       The .ts file format is a simple human-readable XML format that can be used with version control systems if required.

OPTIONS

       -help  Display the usage and exit.

       -noobsolete
	      Drop all obsolete strings.

       -verbose
	      Explain what is being done.

       -version
	      Display the version of lupdate and exit.

USAGE

       Here is an example .pro file that can be given to lupdate:

	   HEADERS	   = funnydialog.h 
			     wackywidget.h
	   SOURCES	   = funnydialog.cpp 
			     main.cpp 
			     wackywidget.cpp
	   FORMS	   = fancybox.ui
	   TRANSLATIONS    = gnomovision_dk.ts 
			     gnomovision_fi.ts 
			     gnomovision_no.ts 
			     gnomovision_se.ts

       When  running lupdate on this project file, the translatable strings in all the files listed in the HEADERS, SOURCES and FORMS entries will
       be put in the translation files listed in the TRANSLATIONS entry. Previous translations will be reused as far as possible,  and	translated
       strings that have vanished from the source files are marked obsolete.

       Lupdate can also be invoked with a list of C++ source files, .ui files and .ts files:

	   lupdate *.cpp *.h *.ui -ts gnomovision_dk.ts

SEE ALSO

       lrelease(1) and http://doc.trolltech.com/i18n.html

Trolltech AS							  18 October 2001							lupdate(1)
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