How to specifically use Teensy's Time.h instead of Arduino built in?

Using Arduino Programming Questions
#1

I wanted to avoid the year 2038 problem when using 32-bit signed time_t type, so that I want to specifically use the Time.h from Teensy (I am writing code for Teensy 3.5).

But the IDE seems to ignore Teensy’s Time.h, in which time_t is defined as

#if !defined(__time_t_defined) // avoid conflict with newlib or other posix libc
typedef unsigned long time_t;
#endif

I find out that no matter what I include, the time_t type I am using is compiled as “long int”. This code reveals that:

time_t t = "ABC";

The compiler will complain:
invalid conversion from ‘const char*’ to ‘time_t {aka long int}’ [-fpermissive]

How to make sure that I am using 32-bit, unsigned time_t?
Also I want when I call now() it’s Teensy’s now() that returns unsigned long time_t, not the built-in long int time_t

Thanks in advance

#2

I’ll assume you’re talking about this library:

On filename case-insensitive operating systems like Windows, there is a problem with the Time.h filename used by that library. An #include directive for Time.h ends up matching to the file time.h from the toolchain. To avoid this problem, the file was renamed TimeLib.h:

So you only need to change your #include directive from:

#include <Time.h>

to:

#include <TimeLib.h>
#3 
#include <TimeLib.h>

I did this but the compiler had the same complaint.

#4

I even tried copying the Teensy's Time folder (GitHub - PaulStoffregen/Time: Time library for Arduino) to my sketch folder, and do this directive:

#include "Time\TimeLib.h"

But still the same, time_t still got overridden by some built-in Arduino definition, compiler shows the same error.

#5

The problem could be with your installed tool chain. Or it could be in your code, which you didn't post. Hard to tell.

#6

Also posted at:

#7

Compiling for an Uno on IDE v1.8.5 this:

#include "TimeLib.h"
time_t xxx = "hello";

void setup() {
}

void loop() {
}

Gives the error message you'd expect:

C:\Users\tr001221\AppData\Local\Temp\arduino_modified_sketch_480339\sketch_jun03a.ino:2:14: warning: invalid conversion from 'const char*' to 'time_t {aka long unsigned int}' [-fpermissive]

 time_t xxx = "hello";
#8

gfvalvo:
The problem could be with your installed tool chain. Or it could be in your code, which you didn’t post. Hard to tell.

This is my entire program:

#include <TimeLib.h>
time_t t = "ABC";
void setup() {
}

void loop() {
}

Board selected is Teensy 3.5

pert:
Also posted at:
https://stackoverflow.com/questions/56426827

Yes, I will also update this forum if I got an answer there :slight_smile:

gfvalvo:
Compiling for an Uno on IDE v1.8.5 this:

#include "TimeLib.h"

time_t xxx = “hello”;

void setup() {
}

void loop() {
}



Gives the error message you'd expect:

C:\Users\tr001221\AppData\Local\Temp\arduino_modified_sketch_480339\sketch_jun03a.ino:2:14: warning: invalid conversion from ‘const char*’ to ‘time_t {aka long unsigned int}’ [-fpermissive]

time_t xxx = “hello”;

I tried an got the same like you for UNO on Arduino 1.8.7.
So this only happens when the board is Teensy. Strange :confused:

#9

mariocaptain:
Yes, I will also update this forum if I got an answer there :slight_smile:

Thanks!

mariocaptain:
So this only happens when the board is Teensy. Strange :confused:

If you turn on warnings (File > Preferences > Compiler warnings) and then compile the following sketch for Teensy 3.5, you can see that the __time_t_defined macro is defined in the toolchain:

#define __time_t_defined foobar
void setup() {}
void loop() {}

:\Users\per\AppData\Local\Temp\arduino_modified_sketch_974617\sketch_jun03a.ino:1:0: warning: "__time_t_defined" redefined

 #define __time_t_defined foobar

 ^

In file included from e:\programfiles\arduinoide\arduino-1.8.8-td\hardware\tools\arm\arm-none-eabi\include\sys\select.h:26:0,

                 from e:\programfiles\arduinoide\arduino-1.8.8-td\hardware\tools\arm\arm-none-eabi\include\sys\types.h:68,

                 from e:\programfiles\arduinoide\arduino-1.8.8-td\hardware\tools\arm\arm-none-eabi\include\stdio.h:61,

                 from E:\ProgramFiles\ArduinoIDE\arduino-1.8.8-td\hardware\teensy\avr\cores\teensy3/Print.h:35,

                 from E:\ProgramFiles\ArduinoIDE\arduino-1.8.8-td\hardware\teensy\avr\cores\teensy3/Stream.h:24,

                 from E:\ProgramFiles\ArduinoIDE\arduino-1.8.8-td\hardware\teensy\avr\cores\teensy3/HardwareSerial.h:252,

                 from E:\ProgramFiles\ArduinoIDE\arduino-1.8.8-td\hardware\teensy\avr\cores\teensy3/WProgram.h:46,

                 from C:\Users\per\AppData\Local\Temp\arduino_build_252405\pch\Arduino.h:6:

e:\programfiles\arduinoide\arduino-1.8.8-td\hardware\tools\arm\arm-none-eabi\include\sys\_timeval.h:41:0: note: this is the location of the previous definition

 #define __time_t_defined

You can see the code in TimeLib.h will only define the time_t type alias if the __time_t_defined macro is not already defined:

#if !defined(__time_t_defined) // avoid conflict with newlib or other posix libc
typedef unsigned long time_t;
#endif
#10

It looks like '__time_t_defined' is already defined when compiling for T3.5 (perhaps other Teensys too). So the conditional:

#if !defined(__time_t_defined) // avoid conflict with newlib or other posix libc
typedef unsigned long time_t;
#endif

is false and 'time_t' is not defined to 'unsigned long'

#11