VS Arduino - undefined reference to vtable for HardwareSerial

Jul 14^th, 2025 at 7:46am (UTC)

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VS Arduino › Visual Micro › Visual Studio 2017, 2019, 2022 › undefined reference to vtable for HardwareSerial

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undefined reference to vtable for HardwareSerial (Read 5489 times)

MacGuyver Newbies Offline Posts: 9 Joined: May 7^th, 2021	undefined reference to vtable for HardwareSerial May 12^th, 2021 at 1:33pm	Print Post
	Updated to the very latest 1.2021.0427. I got the following error on 1.2021.0420 as well. So now I'm getting the following error during Linking: Code Error linking for board P1AM-100 Build failed for project 'IO_Controller' core.a(Uart.cpp.o): In function HardwareSerial::HardwareSerial() HardwareSerial.h:67: undefined reference to vtable for HardwareSerial collect2.exe: error: ld returned 1 exit status Attaching the build output. I used to get this error when I had Core optimization enabled, it went away when I disabled it, and now it's back again.
	« Last Edit: May 12^th, 2021 at 1:34pm by MacGuyver »
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Simon@Visual Micro Administrator Offline Posts: 2728 Joined: Feb 13^th, 2019	Re: undefined reference to vtable for HardwareSerial Reply #1 - May 12^th, 2021 at 2:48pm	Print Post
	When you change the optimization, with Shared Cached Core files, Solution > Clean needs to be run to force the core to recompile. Does this improve if you run Build > Clean Solution, and Rebuild?


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MacGuyver Newbies Offline Posts: 9 Joined: May 7^th, 2021	Re: undefined reference to vtable for HardwareSerial Reply #2 - May 12^th, 2021 at 8:43pm	Print Post
	It doesn't seem to make any difference unfortunately.


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Tim@Visual Micro Administrator Offline Posts: 12191 Location: United Kingdom Joined: Apr 10^th, 2010	Re: undefined reference to vtable for HardwareSerial Reply #3 - May 12^th, 2021 at 11:23pm	Print Post
	Please repost the output. The optimization for the project code was certainly disabled in the verbose output you posted. You can see the -O0 switch in the output when optimization is disabled.


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MacGuyver Newbies Offline Posts: 9 Joined: May 7^th, 2021	Re: undefined reference to vtable for HardwareSerial Reply #4 - May 13^th, 2021 at 11:13am	Print Post
	Ah, I seem to have found the issue. I was relying on the optimization setting from the drop-town toolbar, which apparently is NOT the same as setting the "Disable Optimization [Core/Libraries/Project]" under the properties tab. When I change the optimization from the tool bar dropdown it doesn't change anything. Changing from the properties panels does work. In addition, why is optimization excluding something that is obviously required?

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Tim@Visual Micro Administrator Offline Posts: 12191 Location: United Kingdom Joined: Apr 10^th, 2010	Re: undefined reference to vtable for HardwareSerial Reply #5 - May 13^th, 2021 at 5:14pm	Print Post
	The F4 properties overrides and is based on the current configuration. I think the question about optimization has to be directed at the author of the core. This is because some cores have been designed specifically for the level of optimization the author has set in the platform.txt build instructions. That is what Visual Micro uses by default unless you override it. Out of interest, what was the reason for switching off optimization?


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MacGuyver Newbies Offline Posts: 9 Joined: May 7^th, 2021	Re: undefined reference to vtable for HardwareSerial Reply #6 - May 13^th, 2021 at 9:35pm	Print Post
	I switched off optimization as a test, because it seemed like the only reason a previously working core component would break (hardware serial)


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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #7 - May 24^th, 2021 at 10:23pm	Print Post
	I'm having a very similar problem. The project's .ino file compiles fine with the Arduino IDE, but gives the collect2.exe: error: ld returned 1 exit status ccbs3Ofd.ltrans0.ltrans.o: In function global constructors keyed to 65535_0_FourWD_PulseTurnRateTest.cpp.o.2415 (.text.startup+0x5e): undefined reference to MPU6050::MPU6050(unsigned char) when compiled with VS2019/VM. Verbose compile outputs attached

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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #8 - May 24^th, 2021 at 10:27pm	Print Post
	I haven't made any changes to the optimization settings from the default. The project is a brand-new project created with 'File -> New -> Arduino Project.


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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #9 - May 24^th, 2021 at 10:29pm	Print Post
	Here's the verbose with build properties output

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Simon@Visual Micro Administrator Offline Posts: 2728 Joined: Feb 13^th, 2019	Re: undefined reference to vtable for HardwareSerial Reply #10 - May 25^th, 2021 at 10:53am	Print Post
	Thanks for the detail, and as discussed on Email the remaining C/CPP/H files need to be added to the Project (Right click project > add > Existing Items > Select all missing files > OK). Can you confirm, how you created this project, and whether the C/CPP/H files were present when this was created?


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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #11 - May 25^th, 2021 at 2:36pm	Print Post
	Simon@Visual Micro wrote on May 25^th, 2021 at 10:53am: Thanks for the detail, and as discussed on Email the remaining C/CPP/H files need to be added to the Project (Right click project > add > Existing Items > Select all missing files > OK). Can you confirm, how you created this project, and whether the C/CPP/H files were present when this was created? Thanks for the prompt and complete reply - that did the trick. After all the years I've put in with VS/VM, you'd think I could remember that one I'm pretty sure the C/CPP/H files were NOT present when the project was first created. Thanks again! Frank


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Simon@Visual Micro Administrator Offline Posts: 2728 Joined: Feb 13^th, 2019	Re: undefined reference to vtable for HardwareSerial Reply #12 - May 25^th, 2021 at 3:21pm	Print Post
	Thanks for confirming the fix, and how the project was created. Can we also check how you added the files to the project? 1) Just in File Explorer? 2) Via the Folder View of Solution Explorer in Visual Studio? 3) Another route? (e.g. tabs in Arduino IDE if using both IDEs alongside each other)


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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #13 - May 25^th, 2021 at 3:31pm	Print Post
	Simon@Visual Micro wrote on May 25^th, 2021 at 3:21pm: Can we also check how you added the files to the project? 1) Just in File Explorer? 2) Via the Folder View of Solution Explorer in Visual Studio? 3) Another route? (e.g. tabs in Arduino IDE if using both IDEs alongside each other) 1) Just in file explorer BTW, what was the clue or clues that convinced you the problem was the lack of project references, other than 'missing reference'? Is 'missing reference' the smoking gun? Frank


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Tim@Visual Micro Administrator Offline Posts: 12191 Location: United Kingdom Joined: Apr 10^th, 2010	Re: undefined reference to vtable for HardwareSerial Reply #14 - May 26^th, 2021 at 10:45pm	Print Post
	Yes, especially if files are added outside of VS after the project has first been created/opened. Tip: Did you click the little icon above the solution explorer called "Show all files"? That should show a red exclaimation mark for any files you have added via windows explorer but have not yet set to be "Include in Project"? You can right click the files or folders in that view to "Include in Project" This gives greater control over which files are compiled and also falls in line with how VS works.
	« Last Edit: May 26^th, 2021 at 10:48pm by Tim@Visual Micro »

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FrankP Senior Member Offline Posts: 251 Joined: Oct 19^th, 2011	Re: undefined reference to vtable for HardwareSerial Reply #15 - May 31^st, 2021 at 1:04am	Print Post
	Tim, BTW, created another new Arduino project in VS2019 to create a new version of an existing project. This time I created the project and saved it (which created the folder), then immediately copied all the relevant local files from the old version into the new folder, and added them to the project using the 'Add -> Existing' right-click selection on the project name, then copied in all the code to make the two projects identical except for the name, and it compiled correctly the first time. Thanks again! Frank


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Tim@Visual Micro Administrator Offline Posts: 12191 Location: United Kingdom Joined: Apr 10^th, 2010	Re: undefined reference to vtable for HardwareSerial Reply #16 - May 31^st, 2021 at 2:22am	Print Post
	Great but you can just copy your sources to a new folder (without any .vcxproj files) then click "File>Open>Arduino Project". The "Open Arduino Project" allows you to select the .ino file, then Visual Micro creates a project and automatically adds all the sources.


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