[Solved] Linker Error

Charon117

Hello,

I have a linker problem. When i include "'include "SoftwareKursC.h" it gives me the error "undefined reference to function", which i believe is a linker problem. When i include the source files directly as a *.c everything works.

This is the project: https://drive.google.com/file/d/1WSPILUyRjt3lpc13flTRzAPTJjHyEy_H/view?usp=sharing

Can somebody tell me what i am doing wrong and what the solution to this problem is ? I wouldnt know how to manipulate the qmake file to make it work.

jsulm

@Charon117 said in Linker Error:

INCLUDEPATH +=
%TEMP%

Remove these two lines.

For some reason only main.c file is built. Did you try a complete rebuild:

Delete build folder
Run qmake
Build

Christian Ehrlicher

Apart from the fact that you seem to use qmake to create a makefile - what's the relation to Qt here?
What exact error message do you get?

mchinand

@Charon117 said in Linker Error:

When i include the source files directly as a *.c everything works.

You either have to include the source files in your project or specify in your project file that you will be linking to that library and specifying the location of the library. Can you post your project file?

Charon117

@Christian-Ehrlicher said in Linker Error:

Apart from the fact that you seem to use qmake to create a makefile - what's the relation to Qt here?
What exact error message do you get?

I dont know. I dont know where to begin troubleshooting this. If i wouldnt use qt creator i would simply write make main.o ExercisesWeek1.o etc ..., but since i use qt creator i use qmake, and i wouldnt know how to manipulate qmake to do what i want.

I posted the exact error message. "undefined reference to insert any function of any source file used in main here"

@mchinand said in Linker Error:

@Charon117 said in Linker Error:

When i include the source files directly as a *.c everything works.

You either have to include the source files in your project or specify in your project file that you will be linking to that library and specifying the location of the library. Can you post your project file?

I did include them, and i dont have a library. They are all .c files made into .o files which the linker than cant seem to find to compile.

The drive link includes the whole project, including the pro file. Can you see it ?

The more i think about this the more I am of the oppinion that qmake never creates the .o files for the other source files.

Christian Ehrlicher

I still don't see a relation to Qt here except that you use an IDE which is built with Qt. I also don't get a linker error. If you need the documentation for qmake you can look here but your pro file is correct.

Charon117

@Christian-Ehrlicher said in Linker Error:

I still don't see a relation to Qt here except that you use an IDE which is built with Qt. I also don't get a linker error. If you need the documentation for qmake you can look here but your pro file is correct.

Which leaves me hanging to where the problem is. Is there something else i can provide to troubleshoot this ?

Christian Ehrlicher

@Charon117 said in Linker Error:

Is there something else i can provide to troubleshoot this ?

Post the correct error message and the compiler you use.

Charon117

@Christian-Ehrlicher said in Linker Error:

@Charon117 said in Linker Error:

Is there something else i can provide to troubleshoot this ?

Post the correct error message and the compiler you use.

C:\Users\Name\Desktop\Neuer Ordner\build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug..\SoftwareKursC\main.c:114: error: undefined reference to ExercisesWeek2' debug/main.o: In function main':
C:\Users\Name\Desktop\Neuer Ordner\build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug/../SoftwareKursC/main.c:114: undefined reference to `ExercisesWeek2'

ExercisesWeek2() is the first function that is called in main.

Compiler is MingW 64 bit, version 7.3 i believe.!

Unbenannt6.png

jsulm

@Charon117 said in Linker Error:

ExercisesWeek2() is the first function that is called in main.

And where is it defined? As the error messages says linker can't find its definition. Means: you either did not implement ExercisesWeek2, or you do not link the lib/object file containing ExercisesWeek2.

Charon117

@jsulm said in Linker Error:

@Charon117 said in Linker Error:

ExercisesWeek2() is the first function that is called in main.

And where is it defined? As the error messages says linker can't find its definition. Means: you either did not implement ExercisesWeek2, or you do not link the lib/object file containing ExercisesWeek2.

The question clarifies that replacing the header file *.h with the appropriate *.c files works. This is the content of the header file:

#ifndef SOFTWAREKURSC_H
#define SOFTWAREKURSC_H

void Rechteck(void);
int ExercisesWeek1(void);
int ExercisesWeek2(void);

#endif // SOFTWAREKURSC_H

and Christian Ehrlicher already said that it compiles for him on his system and that the pro file is correct.

Charon117

OK, so i am convinced by now that this is a compiler error, because MingW seems to generate the other *.o objects in %TEMP%, wherever that is. If that is correct, how do i point the Qt Creator to check for %TEMP% ? Also, im not convinced that the object files are actually named correctly ?

So i am not even sure if the compiler generates the object files, where they are, how they are named and how to tell Qt Creator where to find them.

jsulm

@Charon117 said in Linker Error:

i am convinced by now that this is a compiler error

"undefined reference to" - is a linker error.

Please post the pro file and the whole build log of a complete rebuild.

Charon117

@jsulm said in Linker Error:

@Charon117 said in Linker Error:

i am convinced by now that this is a compiler error

"undefined reference to" - is a linker error.

Please post the pro file and the whole build log of a complete rebuild.

the drive link i posted contains the whole project. Can you see it ?

I dont know what the whole build log is, or where to find it, but i posted a picture here

Unbenannt6.png

jsulm

@Charon117 said in Linker Error:

the drive link i posted contains the whole project

I can't access it. pro file is just text, easy to post here...
Build log: all compiler and linker calls during the build. In QtCreator see "4 Compile Output" tab at the bottom.

Charon117

@jsulm said in Linker Error:

@Charon117 said in Linker Error:

the drive link i posted contains the whole project

I can't access it. pro file is just text, easy to post here...
Build log: all compiler and linker calls during the build. In QtCreator see "4 Compile Output" tab at the bottom.

Why cant you access it ?

SoftwareKursC.pro:
TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

INCLUDEPATH +=
%TEMP%

SOURCES +=
ExercisesWeek1.c
ExercisesWeek2.c
Rechteck.c
main.c

HEADERS +=
SoftwareKursC.h

Tab4 output:
15:10:25: Running steps for project SoftwareKursC...
15:10:25: Configuration unchanged, skipping qmake step.
15:10:25: Starting: "C:\Coding\Qt\Tools\mingw810_64\bin\mingw32-make.exe" -j4
C:/Coding/Qt/Tools/mingw810_64/bin/mingw32-make -f Makefile.Debug
mingw32-make[1]: Entering directory 'C:/Users/Name/Desktop/Neuer Ordner/build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug'
gcc -c -fno-keep-inline-dllexport -g -Wall -Wextra -Wextra -DUNICODE -D_UNICODE -DWIN32 -DMINGW_HAS_SECURE_API=1 -DQT_QML_DEBUG -I..\SoftwareKursC -I. -I%TEMP% -IC:\Coding\Qt\5.15.2\mingw81_64\mkspecs\win32-g++ -o debug\main.o ..\SoftwareKursC\main.c
..\SoftwareKursC\main.c: In function 'inputSales':
..\SoftwareKursC\main.c:18:25: warning: unused parameter 'ABC' [-Wunused-parameter]
void inputSales(double* ABC){
^
..\SoftwareKursC\main.c: In function 'readText':
..\SoftwareKursC\main.c:106:9: warning: unused variable 'symbol' [-Wunused-variable]
int symbol = getchar();
^~
..\SoftwareKursC\main.c:104:20: warning: unused parameter 'smallLettersCount' [-Wunused-parameter]
void readText(int *smallLettersCount, int *capitalLettersCount, int *whiteSpaceCount){
~^~~~~~~~~~~
..\SoftwareKursC\main.c:104:44: warning: unused parameter 'capitalLettersCount' [-Wunused-parameter]
void readText(int *smallLettersCount, int *capitalLettersCount, int *whiteSpaceCount){
~^~~~~~~~~~~~~~~
..\SoftwareKursC\main.c:104:70: warning: unused parameter 'whiteSpaceCount' [-Wunused-parameter]
void readText(int *smallLettersCount, int *capitalLettersCount, int *whiteSpaceCount){
~^~~~~~~~~~~
..\SoftwareKursC\main.c: In function 'main':
..\SoftwareKursC\main.c:136:19: warning: format '%ld' expects a matching 'long int' argument [-Wformat=]
printf("%ld" );
^
..\SoftwareKursC\main.c:136:19: warning: format '%ld' expects a matching 'long int' argument [-Wformat=]
..\SoftwareKursC\main.c: In function 'Exercise':
..\SoftwareKursC\main.c:74:5: warning: 'i' is used uninitialized in this function [-Wuninitialized]
for(int i; i < count;){
^
g++ -Wl,-subsystem,console -mthreads -o debug\SoftwareKursC.exe debug/main.o
debug/main.o: In function main': C:\Users\\Desktop\Neuer Ordner\build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug/../SoftwareKursC/main.c:114: undefined reference to ExercisesWeek2'
C:\Users\Name\Desktop\Neuer Ordner\build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug/../SoftwareKursC/main.c:116: undefined reference to `ExercisesWeek1'
collect2.exe: error: ld returned 1 exit status
mingw32-make[1]: *** [Makefile.Debug:68: debug/SoftwareKursC.exe] Error 1
mingw32-make[1]: Leaving directory 'C:/Users/Name/Desktop/Neuer Ordner/build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug'
mingw32-make: *** [Makefile:45: debug] Error 2
15:10:26: The process "C:\Coding\Qt\Tools\mingw810_64\bin\mingw32-make.exe" exited with code 2.
Error while building/deploying project SoftwareKursC (kit: Desktop Qt 5.15.2 MinGW 64-bit)
When executing step "Make"
15:10:26: Elapsed time: 00:01.

jsulm

@Charon117 said in Linker Error:

INCLUDEPATH +=
%TEMP%

Remove these two lines.

For some reason only main.c file is built. Did you try a complete rebuild:

Delete build folder
Run qmake
Build

mchinand

You have to escape (add a backslash, \) the newlines so the list of source files will be treated as a single input line. See the SOURCES example here: https://doc.qt.io/qt-5/qmake-project-files.html#variables

Christian Ehrlicher

I really wonder why you upload a project but then don't use the pro-file which is in there which is correct...

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += \
        ExercisesWeek1.c \
        ExercisesWeek2.c \
        Rechteck.c \
        main.c

HEADERS += \
    SoftwareKursC.h

Charon117

@jsulm said in Linker Error:

@Charon117 said in Linker Error:

INCLUDEPATH +=
%TEMP%

Remove these two lines.

For some reason only main.c file is built. Did you try a complete rebuild:

Delete build folder

Run qmake

Build

Ok, so the weirdest thing happened. It works now.

No clue how that happened, or what i did to change it. But ... lol ... check this out.

I delete the whole build folder, eg.
build-SoftwareKursC-Desktop_Qt_5_15_2_MinGW_64_bit-Debug

Then i compile with Qt Creator, and i only use #include *.c files. Then i comment out the *.c includes and enable the *.h includes. This leads us to exactly the error i described.

Another delete later:
I compile this time with *.h files and then change them to *.c files. I get a completely different linker error, but a linker error nonetheless.

Another delete:
I only compile with *.h includes and it works. No changing afterwards.

Another delete:
I only compile with *.c includes and it works. No changing afterwards.

Conclusion:
Changing compilation from *.h to *.c includes leads to linker errors, as well as changes from *.c to *.h includes. Deleting the build folder in both cases is the solution.

What kind of clusterfucking mindblowing error is this ?

Thanks for the help, i guess i will mark this as solved. Thanks to @jsulm for suggesting the correct solution. I will make a note that in case of mysterious bugs deleting the build folder is priority number one. If somebody has an explanation of why this is happening they can add it as another post.

Thank you all for participating in this discussion.