CODEWITHSUNDEEP
c++qt-creatorlinker-errorsiconvzbar
sashoalm
sashoalm

Reputation: 79527

Error when statically-linking to libzbar.a: undefined reference to `_imp__GetACP@0'

I link to zbar from my program. I've built zbar using mingw/msys. My application is built using Qt Creator.

When I link dynamically to zbar using libzbar.dll.a, it compiles and runs fine. When I link to libzbar.a, building my application fails with a linker error:

C:/Qt/Tools/mingw491_32/bin/../lib/gcc/i686-w64-mingw32/4.9.1/../../../../i686-w64-mingw32/lib/../lib/libiconv.a(localcharset.o):localcharset.c:(.text+0x7): undefined reference to `_imp__GetACP@0'
collect2.exe: error: ld returned 1 exit status

This convoluted path - C:/Qt/Tools/mingw491_32/bin/../lib/gcc/i686-w64-mingw32/4.9.1/../../../../i686-w64-mingw32/lib/../lib/libiconv.a - resolves to C:\Qt\Tools\mingw491_32\i686-w64-mingw32\lib\libiconv.a. So it seems that Qt Creator is trying to link against its own libiconv.a, which is missing some functions that libzbar.a needs to use.

I'm not sure how to make Qt Creator use the msys libiconv.a, I tried this:

LIBS += c:/mingw/lib/libiconv.a
LIBS += $$PWD/zbar/lib/libzbar.a

But it had no effect, I'm getting the same error. How do I convince Qt Creator to use c:/mingw/lib/libiconv.a instead of its own version?

Edit: Here is the smallest code that reproduces the error:

#define NULL 0
#include <zbar.h>
int main()
{
    zbar::ImageScanner scanner;
    return 0;
}

And in the .pro file I have:

INCLUDEPATH += c:/MinGW/msys/1.0/local/include
LIBS += -Lc:/MinGW/msys/1.0/local/lib -lzbar

Upvotes: 3

Views: 2272

Answers (2)

sashoalm
sashoalm

Reputation: 79527

Many thanks to @skypjack, his solution works. I'll only add some things I found out by testing it:

PRE_TARGETDEPS was not really necessary, those 3 lines are sufficient to make the project compile:

INCLUDEPATH += c:/MinGW/msys/1.0/local/include
LIBS += c:/MinGW/msys/1.0/local/lib/libzbar.a
LIBS += c:/MinGW/lib/libiconv.a

Which was strange because I distinctly remember trying this even before posting my question on SO. But after swapping the last 2 lines:

INCLUDEPATH += c:/MinGW/msys/1.0/local/include
LIBS += c:/MinGW/lib/libiconv.a
LIBS += c:/MinGW/msys/1.0/local/lib/libzbar.a

the error returned. I had indeed put libiconv.a before libzbar.a, so the error really was because of link-order.

Edit: In the end, it worked even with Qt Creator's own libiconv, it was just that I needed to add it after zbar:

LIBS += -Lc:/MinGW/msys/1.0/local/lib -lzbar -liconv

Upvotes: 3

skypjack
skypjack

Reputation: 50550

Try with a .pro file like the following one:

TEMPLATE=app
TARGET=appname
SOURCES=main.cpp
PRE_TARGETDEPS += c:/MinGW/msys/1.0/local/lib/libzbar.a
PRE_TARGETDEPS += c:/MinGW/msys/1.0/local/lib/libiconv.a
INCLUDEPATH += c:/MinGW/msys/1.0/local/include
win32:LIBS += c:/MinGW/msys/1.0/local/lib/libzbar.a
win32:LIBS += c:/MinGW/msys/1.0/local/lib/libiconv.a
// ... continue

Upvotes: 1

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