math function failing

[goswami]

I have got a project sample from one cmake user. When I am trying to build the same in my PC I am getting lots of error over undefined reference of math function defined in math.h file. A sample as " :-1: error:-----FMI_Stdalone_Bool_multi_proj/Bool_Multi/sources/dsblock5.c:342: undefined reference to `floor'".
Can anybody throw some light why the same is happening despite math.h is included in the same file?
I also require a bit of help on community help over Qt. I am only getting mail as help can be extended on commercial license. I am pursuing Qt purely for self education. Is there anyway to know what to do if no response is given in the forum?

[mrjj]

Hi
-Can anybody throw some light why the same is happening despite math.h is included in the same file?

Well if you are not on the same platform, it can be that Cmake cant find the math lib to link against.

• . Is there anyway to know what to do if no response is given in the forum?

There are other coding places to ask also. Like StackOverflow.
But make sure you write good questions as it's impossible to help if clear information is not
provided.

But normally we do answer most questions here :)

[SGaist]

Hi,

I would say that you are missing std:: before your floor calls.

[goswami]

@mrjj Thank you for taking up my call. I tried with a small program with math.h and cmake. It is working alright. Hence not sure why same is failing for the FMI one.

[goswami]

@SGaist The code is auto generated by a tool called Dymola. They insist for Visual Studio but I wanted to try on Qt Creator. It is appearing linking failure. The error message in Qt Creator is as below
:-1: error: CMakeFiles/app.dir/Bool_Multi/sources/all.c.o: in function ModelicaInternal_temporaryFileName': :-1: error: CMakeFiles/app.dir/Bool_Multi/sources/all.c.o: in function Mat_VarDelete':
:-1: error: CMakeFiles/app.dir/Bool_Multi/sources/all.c.o: in function divideDymola': /home/skgoswami/Desktop/DymolaTest/FMI_Stdalone_Bool_multi_proj/Bool_Multi/sources/dsutil.h:789: error: undefined reference to floor'
:-1: error: /home/skgoswami/Desktop/DymolaTest/FMI_Stdalone_Bool_multi_proj/Bool_Multi/sources/dsutil.h:789: undefined reference to ceil' :-1: error: CMakeFiles/app.dir/Bool_Multi/sources/all.c.o: in function modulusDymola':
/home/skgoswami/Desktop/DymolaTest/FMI_Stdalone_Bool_multi_proj/Bool_Multi/sources/dsutil.h:792: error: undefined reference to `floor'

[SGaist]

Visual Studio designate both the IDE and the set of tools, Qt Creator is just an IDE.

But it looks like you are working on Linux so can you explain your environment ?

[goswami]

I exactly could not understand what you meant by environment. Yes mine is ubuntu 20.04.4, Qt creator 7.0.2, cmake 3.21.1. gcc by default 64bit. The builder is being used 'ninja' by default. I found users faced problem with math.h linking. However I am not getting any problem if I make a simple program as reported by those users. However error is same undefined reference. Incidentally the application is C and hence std:: is not acceptable. I am better providing the content of CMakeLists.txt file for your ready reference below

cmake_minimum_required (VERSION 3.7)
set (MODEL_NAME Bool_Multi)
project (Bool_Multi LANGUAGES C)
add_executable(app
include/fmi2Functions.h
include/fmi2FunctionTypes.h
include/fmi2TypesPlatform.h
src/bool_multi.c
Bool_Multi/sources/all.c
)
target_include_directories(app PUBLIC
include
Bool_Multi/sources
)

[SGaist]

From the looks of it, you are not linking to the math library.

[goswami]

@SGaist Yes but why so is not clear. Single file with math.h is working OK. Where the linker related setting and how it can be fixed is my question.

[goswami]

@mrjj it is linking time problem undestood but do not know how to fix it in Qt. Single file with #include<math.h> is working alright. Pl. advise if any other sources to explore for the solution.

[JonB]

@goswami
Please show the linker line being executed. So far as I am aware, linking with math library is achieved via -lm option.

[goswami]

@JonB I am using Qt IDE with cmake for building. Following code is working alright
#include <stdio.h>
#include <math.h>
int main()
{
printf("Hello World!=%f\n",pow(2.0,2.0));
return 0;
}
And CMakeLists.txt content is as below
cmake_minimum_required(VERSION 3.5)
project(untitled1 LANGUAGES C)
add_executable(untitled1 main.c)
I do not know how to check linker option in Qt IDE. This is reasonably big project and impossible to go for command line building.

[JonB]

@goswami said in math function failing:

I do not know how to check linker option in Qt IDE

Did you try looking in the Build Output pane? I don't know, that would be my guess. And I don't know about cmake so I'll leave you with others to respond.

[goswami]

@JonB Thanks for trying to help.

[SGaist]

target_link_libraries(untitled1 m)

[goswami]

@SGaist said in math function failing:

target_link_libraries(untitled1 m)

Many thanks all math.h related errors have gone and the application is giving output. Can you throw some light why the same is not failing when only one file with math.h include is there? Another as it is appearing all #include of libraries are not creating problem. Is it system dependant viz. may compile in one environment but fail in somewhere?
I am really grateful over the efforts you have put to help me out of this crisis which became a serious bottleneck for progress to next stage.

[SGaist]

It depends on the library and what is used of them.

Some are header only, some are template based so it really depends on what you use from these and how they are implemented. It's usually not tied to a specific OS.

[goswami]

@SGaist Thank you very much for updating me.