C++ FatFs undefined reference to functions - c++

Question

I have a code written in Atmel Studio to read/write data from a SD card. I am using FatFs here. My problem is the code doesn't compile when I use some of the functions (f_chdir, f_getcwd...) in FatFs. Some functions works fine (f_puts, f_open, f_mount, f_mkdir...). All these functions are located in same header file (ff.h, ff.c)
The error says "undefined reference to -function-, ld returned 1 exit status". When I go to the error it shows the end of the code while it is suppose to show where the error is.
I cannot understand the problem with my code. Any help is appreciated.

Answer 1

Just ran into this using the SD card for a project using SAM4S Xplained Pro (Atmel 7, ASF 3.20).
Make sure you have all the asf projects (fatfs, sd_mmc, memory access control, and then the other basics e.g. pmc, gpio, and maybe a few more). My asf did NOT include sd_mmc_mem.c and sd_mmc_mem.h for some reason, so I had to include those myself. Also remember to do the sd_mmc_init() at the top of your main loop. As for the configuration...
If you look closely at ffconf.h, the first thing it does is include conf_fatfs.h, which (wait for it!) is EXACTLY the same file line by line as ffconf.h. All the variables are defined there first and foremost (and guarded by an #ifndef FFCONF and NOT an CONF_FATFS) aka that's where it counts..
Go into conf_fatfs.h and change _USE_STRFUNC to 1 or 2 et voila.
Also note that in the places where you use it, you'll have to #include the ff.h preceded by either ffconf.h or conf_access.h
ASF is a real snake pit if you don't know what you're looking for.
Enjoy.

Answer 2

By default, the memory control access interface is disabled in the ASF wizard. In order to enable the memory control access, please follow the steps below.
Open the ASF wizard (Alt + W).
Enable the Memory Control Access as follows.
ASF SD sd_mmc_mem.h memory access enable
Finally, click the “Apply” option to make the changes.
This adds sd_mmc_mem.h /.c files

Answer 3

Open the ffconf.h in your favorite editor and set _FS_RPATH to 2. From ffconf.h:
#define _FS_RPATH 0
/* This option configures relative path feature.
/
/ 0: Disable relative path feature and remove related functions.
/ 1: Enable relative path feature. f_chdir() and f_chdrive() are available.
/ 2: f_getcwd() function is available in addition to 1.
/
/ Note that directory items read via f_readdir() are affected by this option. */
Which features of the fatfs library are included in your build is configurable, so that you don't have to lose valuable ROM space (as well as a few bytes of RAM) for functions you're not using.
For versions of the FatFS library prior to 0.8a, _FS_RPATH supports only values 0 and 1; f_getcwd is not available in these versions.
Additionally, in versions prior to 0.8, it is necessary for C++ code to explicitly include its headers as C headers to avoid name mangling:
extern "C" {
#include "ff.h"
}
From version 0.8 onwards, it does this internally. You can find the new versions here if you're still working with an old one -- the comment you left leads me to believe that this might be the case.

Answer 4

Check if _FS_MINIMZE in ffconf.h is 0 to have all functions available.
In my version that I downloaded from elm-chan it was by default set to 3 and lead to the compiler error: undefined reference.

Answer 5

In file ffconf.h, set #define _USE_FIND to 1.
/* This option switches filtered directory read functions, f_findfirst() and
/ f_findnext(). (0:Disable, 1:Enable 2:Enable with matching altname[] too) */
I needed to use f_findfirst() and f_findnext() functions and i was getting undefined reference errors.
Now this solved my problem.

Answer 6

Drive/directory handling functions are under #if _FS_RPATH >= 1 (or similar preprocessors) .