VS Arduino - Linker error when function is implemented in extern file .c

Jun 14^th, 2025 at 12:37pm (UTC)

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VS Arduino › › › Linker error when function is implemented in extern file .c

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Linker error when function is implemented in extern file .c (Read 3562 times)

zimka Newbies Offline Posts: 1 Joined: May 19^th, 2015	Linker error when function is implemented in extern file .c May 19^th, 2015 at 7:15am	Print Post
	Hello. I've got some trouble with linker in Atmel Studio 6.2, Arduino ProMicro Leonardo, Arduino 1.6 IDE. I tried to write simple project for blinking with one header and one .c file. blink2.ino: Code (C++) #include "testc.h" void setup() { pinMode(17, OUTPUT); //Time = 500; //Step = 100; initTime(); } void loop() { digitalWrite(17, HIGH); delay(1000); Time += Step; digitalWrite(17, LOW); delay(Time); } testc.h: Code (C++) #ifndef _TESTC_h #define _TESTC_h #if defined(ARDUINO) && ARDUINO >= 100 #include "arduino.h" #else #include "WProgram.h" #endif int Time; int Step; void initTime(void); int giveTime(void); #endif Code (C++) #include "testc.h" void initTime() { Time = 500; Step = 100; return; } int giveTime() { Time += Step; return Time; } I get an error when I try to use functions from testc.c, but it is working without problems when I only use variables from testc.h and don't use functions; Code Compiling 'blink2' for 'Arduino Leonardo' Build folder: file:///C:/Users/zimka/AppData/Local/V.Micro/Arduino/Builds/blink2/leonardo Summary: Header=1 Prototypes=3 Imports=0 Additional Defines: Architecture Tools: C:\Program Files (x86)\Arduino/hardware/tools/avr/bin/ GCC: 4.8.1 Sketchbook: file:///C:/Program%20Files%20(x86)/Arduino/examples Core Include Paths Include Path 'C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino' Include Path 'C:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\leonardo' "C:\Program Files (x86)\Arduino/hardware/tools/avr/bin/avr-gcc" -c -g -Os -w -ffunction-sections -fdata-sections -MMD -mmcu=atmega32u4 -DF_CPU=16000000L -DARDUINO=160 -DARDUINO_AVR_LEONARDO -DARDUINO_ARCH_AVR -DUSB_VID=0x2341 -DUSB_PID=0x8036 -DUSB_MANUFACTURER= -DUSB_PRODUCT="\"Arduino Leonardo\"" -I"C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino" -I"C:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\leonardo" "C:\Users\zimka\AppData\Local\V.Micro\Arduino\Builds\blink2\leonardo\testc.c" -o "C:\Users\zimka\AppData\Local\V.Micro\Arduino\Builds\blink2\leonardo\testc.c.o" "C:\Program Files (x86)\Arduino/hardware/tools/avr/bin/avr-g++" -c -g -Os -Wall -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -mmcu=atmega32u4 -DF_CPU=16000000L -DARDUINO=160 -DARDUINO_AVR_LEONARDO -DARDUINO_ARCH_AVR -DUSB_VID=0x2341 -DUSB_PID=0x8036 -DUSB_MANUFACTURER= -DUSB_PRODUCT="\"Arduino Leonardo\"" -I"C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino" -I"C:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\leonardo" -o o" Build Core Paths: C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino "C:\Program Files (x86)\Arduino/hardware/tools/avr/bin/avr-gcc" -w -Os -Wl,--gc-sections -mmcu=atmega32u4 -o "C:\Users\zimka\AppData\Local\V.Micro\Arduino\Builds\blink2\leonardo\testc.c.o" o" "C:\Users\zimka\AppData\Local\V.Micro\Arduino\Builds\blink2\leonardo/core.a" "-LC:\Users\zimka\AppData\Local\V.Micro\Arduino\Builds\blink2\leonardo" -lm blink2.cpp.o:In function `setup' collect2*:error: ld returned 1 exit status Error creating .elf Thanks.


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Tim@Visual Micro Administrator Offline Posts: 12191 Location: United Kingdom Joined: Apr 10^th, 2010	Re: Linker error when function is implemented in extern file .c Reply #1 - May 19^th, 2015 at 11:30am	Print Post
	Hi Zimka, Thanks for the clear report. Your code is invalid so the error is correct although I will look into a better error report. Are you new to Arduino? I think the initTime() needs to be public or external, why not use .cpp with real class or another .ino? Otherwise make sure you use external or some other means to declare your c methods Thanks
	« Last Edit: May 19^th, 2015 at 11:30am by Tim@Visual Micro »

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