Ld problems with multiple source files

DrN · May 14, 2025, 3:44pm

Hi,

I am trying to compile a sketch with some additional c language files in the same directory. The compile and ld seems to miss the extra files.

How do I fix that?

Here is a directory listing from the directory containing my

$ ls -1
flexpwm_auxiliary.c
flexpwm_auxiliary.h
LCCD_Controller_250514.ino

And here is the output from the compile and link,

/home/nelson/.arduino15/packages/teensy/tools/teensy-compile/11.3.1/arm/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /home/nelson/.cache/arduino/sketches/4636C8904CF489ED832AFE7140B4A5E6/sketch/LCCD_Controller_250514.ino.cpp.o: in function `loop':
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/LCCD_Controller_250514.ino:3211: undefined reference to `pwm_baseaddr(unsigned char)'
/home/nelson/.arduino15/packages/teensy/tools/teensy-compile/11.3.1/arm/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/LCCD_Controller_250514.ino:3212: undefined reference to `pwm_submodule(unsigned char)'
/home/nelson/.arduino15/packages/teensy/tools/teensy-compile/11.3.1/arm/bin/../lib/gcc/arm-none-eabi/11.3.1/../../../../arm-none-eabi/bin/ld: /home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/LCCD_Controller_250514.ino:3213: undefined reference to `pwm_channel(unsigned char)'
collect2: error: ld returned 1 exit status
exit status 1

Compilation error: exit status 1

DrN · May 14, 2025, 5:53pm

After posting this, I recalled that the IDE picks up .cpp files, not .c files in the sketch directory.

Is there a way to get around that behavior, other than renaming .c files to .cpp?

oqibidipo · May 14, 2025, 7:50pm

You need extern "C" to tell the C++ compiler that the functions are written in C.

Modify the header file like this:

#ifdef __cplusplus
extern "C" {
#endif

// C function prototypes here

#ifdef __cplusplus
}
#endif

Explanation: the C++ compiler mangles the function names to include parameter types, e.g. pwm_submodule(unsigned char) becomes _Z13pwm_submoduleh.

Incorrect, .c files are compiled as well.

DrN · May 14, 2025, 8:14pm

Thank you, that works. But now my Serial.print() inside of the .c file, are undefined.

Is there an easy fix for that?

/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c: In function 'printbits16_':
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c:161:5: error: 'Serial' undeclared (first use in this function)
  161 |     Serial.print((u16>>bits)&1);
      |     ^~~~~~
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c:161:5: note: each undeclared identifier is reported only once for each function it appears in
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c: In function 'pwm_dump':
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c:182:3: error: 'Serial' undeclared (first use in this function)
  182 |   Serial.print("PWM pin");
      |   ^~~~~~
/home/nelson/Projects/TeensyDataAcquistion/SPI_Instrumenation_Project/Firmware/LCCD_Controller_250514/flexpwm_auxiliary.c:200:57: error: 'BIN' undeclared (first use in this function)
  200 |   Serial.print( "MCTRL2 MONPLL "); Serial.print(u16&0XF,BIN);
      |                                                         ^~~
exit status 1

Compilation error: 'Serial' undeclared (first use in this function)

DrN · May 14, 2025, 8:18pm

Here are the .c and .h files. This is meant to add some functionality to the Teensy 4 pwm support, to facilitate low level access to the PWM registers.

flexpwm_auxiliary.c (10.0 KB)
flexpwm_auxiliary.h (360 Bytes)

DrN · May 14, 2025, 8:22pm

An now another odd behavior.

I renamed the file back to .cpp. But the compile and ld still finds the now non-existent .c file!!!

DrN · May 14, 2025, 8:31pm

So... I found the cache and manually deleted it. There must be some way to do this in a more organized or systematic way in the IDE.

If it is necessary to delete the cache when files are renamed, would that not seem to qualify as a bug or design error? It is certainly a foreseeable use case.

ptillisch · May 14, 2025, 9:44pm

It is absolutely a bug. The Arduino developers are tracking the bug here:

github.com/arduino/arduino-cli

Previous file persists in build folder after renaming non-`.ino` sketch code file

opened 11:18PM - 19 Jun 16 UTC

digimeas

topic: code type: imperfection topic: build-process

### Describe the problem The previous file persists in the sketch build folder …after a sketch code file with extension other than `.ino`/`.pde` is renamed. 🐛 This can result in spurious compilation errors or confusing bugs. Arduino CLI users can work around the bug by adding the `--clean` flag to their command, but the only workaround for Arduino IDE users is to manually clean the build folder. ### To reproduce ```text $ arduino-cli version arduino-cli.exe Version: git-snapshot Commit: a735ddfd Date: 2023-01-15T01:00:07Z $ arduino-cli sketch new /tmp/FooSketch $ echo "void asdf() {}" > /tmp/FooSketch/foo.cpp $ arduino-cli compile --fqbn arduino:avr:uno /tmp/FooSketch [...] $ mv /tmp/FooSketch/foo.cpp /tmp/FooSketch/bar.cpp $ arduino-cli compile --fqbn arduino:avr:uno /tmp/FooSketch C:\Users\per\AppData\Local\Temp\arduino\sketch-2405C4C9F90028537C79B0744BCE536E\sketch\foo.cpp.o (symbol from plugin): In function `asdf()': (.text+0x0): multiple definition of `asdf()' C:\Users\per\AppData\Local\Temp\arduino\sketch-2405C4C9F90028537C79B0744BCE536E\sketch\bar.cpp.o (symbol from plugin):(.text+0x0): first defined here collect2.exe: error: ld returned 1 exit status Used platform Version Path arduino:avr 1.8.6 C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.6 Error during build: exit status 1 $ ls "C:/Users/per/AppData/Local/Temp/arduino/sketch-2405C4C9F90028537C79B0744BCE536E/sketch" bar.cpp bar.cpp.d bar.cpp.o foo.cpp foo.cpp.d foo.cpp.o FooSketch.ino.cpp FooSketch.ino.cpp.d FooSketch.ino.cpp.o ``` 🐛 `foo.cpp` is still present in the build folder even though not present in the sketch. `foo.cpp` is compiled in addition to `bar.cpp` and the primary sketch file. ### Expected behavior Files are always removed from the sketch build folder when no longer present in the sketch. ### Arduino CLI version #### Original report Arduino IDE 1.6.9 #### Last verified with 0.34.1 ### Operating system - Linux - Windows ### Operating system version - Mint - 10 ### Additional context #### Workaround <a name="workaround-cli"></a> ##### Arduino CLI users Run an `arduino-cli compile` command with [the `--clean` flag](https://arduino.github.io/arduino-cli/dev/commands/arduino-cli_compile/#options). <a name="workaround-ide"></a> ##### Arduino IDE users 1. Examine the compiler error message. It will show the path of the temporary build folder. For example, in this error: ```text C:\Users\per\AppData\Local\Temp\arduino\sketches\7930E8409AED6D4F4A4782CF985194E9\sketch\foo.cpp.o (symbol from plugin): In function `asdf()': (.text+0x0): multiple definition of `asdf()' C:\Users\per\AppData\Local\Temp\arduino\sketches\7930E8409AED6D4F4A4782CF985194E9\sketch\bar.cpp.o (symbol from plugin):(.text+0x0): first defined here collect2.exe: error: ld returned 1 exit status exit status 1 Compilation error: exit status 1 ``` The temporary build folder is: ```text C:\Users\per\AppData\Local\Temp\arduino\sketches\7930E8409AED6D4F4A4782CF985194E9\sketch\ ``` 1. Delete the temporary build folder. #### Additional reports - https://github.com/arduino/arduino-cli/issues/1699 - https://github.com/arduino/arduino-cli/issues/2058 - https://github.com/arduino/arduino-cli/issues/2613 - https://github.com/arduino/arduino-cli/issues/2870 - https://github.com/arduino/arduino-ide/issues/970 - https://github.com/arduino/arduino-ide/issues/1316 - https://github.com/arduino/arduino-ide/issues/1691 - https://github.com/arduino/arduino-ide/issues/2323 - https://github.com/arduino/arduino-ide/issues/482#issuecomment-2188269824 - https://github.com/arduino/Arduino/issues/2072 - https://forum.arduino.cc/t/ide-and-compiler-clear/1077526 - https://forum.arduino.cc/t/changed-tab-name-in-sketch-still-linking-old-o-file/1046286 - https://forum.arduino.cc/t/weird-error-pointing-to-old-code/1113608 - https://forum.arduino.cc/t/ide2-bit-upset-need-help/1129513 - https://forum.arduino.cc/t/renamed-tabs-wont-go-away/1165338 - https://forum.arduino.cc/t/file-renaming-issue/1173234/6 - https://forum.arduino.cc/t/reorganizing-code-w-wire-h-library/1180211 - https://forum.arduino.cc/t/ide-not-recognising-file-type-change-from-c-to-cpp/1215993 - https://forum.arduino.cc/t/code-compiles-in-old-ide-but-not-the-new-one/1286767 - https://forum.arduino.cc/t/problem-while-defining-namespaces-with-it-own-cpp-and-hpp-files/1304403 - https://forum.arduino.cc/t/there-is-a-bug-in-the-wire-library-for-version-1-8-6-avr-boards/1336297/18 - https://forum.arduino.cc/t/new-version-of-arduino-ide-2-3-5-error/1371224/20 - https://forum.arduino.cc/t/how-to-clear-cache-from-ide/1374114 - https://forum.arduino.cc/t/ld-problems-with-multiple-source-files/1381506/6 --- <details> <summary><b>Keywords</b></summary> <p> - rename - header - .h - .cpp - .c - C++ </p> </details> ### Issue checklist - [X] I searched for previous reports in [the issue tracker](https://github.com/arduino/arduino-ide/issues?q=) - [X] I verified the problem still occurs when using the latest [nightly build](https://www.arduino.cc/en/software#nightly-builds) - [X] My report contains all necessary details

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Please only comment on the GitHub issue thread if you have new technical information that will assist with the resolution. General discussion and support requests are always welcome here on the Arduino Forum.

DrN · May 14, 2025, 10:59pm

Great. So in other words, the answer to the question "how do we clear the cache", is that we should not need to clear the cache.

Still, that would seem to be an important function to have in the ide.

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