Passing a vector object by reference to a function loses values

[dzalf]

Hi there

I am trying to implement an SDCard reader of the filenames inside of it by using Vector of const char* as follows.

When I pass the vector by reference, I can retrieve the total number of elements found, HOWEVER, the const char* elements with the filenames are lost.

I have tried reassigning a storage array inside the function, passing pointers, returning another vector by copy, returning pointers, etc. No luck

#include "Vector.h"
#include "SD.h"

#define DEBUG_PRINT(x) (debug->print(x))
#define DEBUG_PRINTLN(x) (debug->println(x))

const int FILES_IN_CARD_VECTOR_SIZE = 50;
char debugBuffer[100];

typedef Vector<const char*> SDCardFiles;

SDCardFiles  filesInCard;
const char* filesInCardStorage[FILES_IN_CARD_VECTOR_SIZE];

void setup(){

    filesInCard.begin();
    filesInCard.setStorage(filesInCardStorage);

    File root = SDCard.open("/");
    retrieveSDCardFilenames(root, filesInCard);

    DEBUG_PRINT(F("Files in card: "));
    DEBUG_PRINTLN(filesInCard.size());

        for (size_t ptr = 1; ptr <= filesInCard.size(); ptr++)
        {
            // here only rubbish gets printed
            sprintf(debugBuffer, "%d. %s\n", ptr, filesInCard.at(ptr - 1));
            DEBUG_PRINTLN(debugBuffer);
        }
}

where the skimmed version of the function retrieveSDCardFilenames is:

void retrieveSDCardFilenames(File folder, SDCardFiles &filesVector)
{
    int fileCount = 0;

    while (true)
    {
        File entry = folder.openNextFile();

        if (!entry)
        {
            folder.rewindDirectory();
            break;
        }
        else
        {
            fileCount++;
        }
        entry.close();
    }

    for (int i = 0; i < fileCount; i++)
    {

        File document = folder.openNextFile();

        const char *fn = (const char *const)document.name();

        DEBUG_PRINT(i + 1);
        DEBUG_PRINT(". Fn >> ");
        DEBUG_PRINTLN(fn);

        // printing names here is OK!

        filesVector.push_back((const char *const)document.name());

         sprintf(debugBuffer, "%d. %s\n", i+1, filesVector.at(i));
          DEBUG_PRINTLN(debugBuffer);

        // this printout is OK too!

        document.close();
    }

}

This is a section of the serial console with the result that I am getting. I can see the elements from the vector passed by reference inside of the functions, however, they are lost out of its scope, however, I am passing it by reference.

Please ignore the two lines that read:

Files created:
MIS1_003.txt
MIS2_006.txt

as these belong to another section of my code that DOES work fine using vectors from this library.

Any ideas?

[dzalf]

On a strange turn of events, I can confirm that my code fails ONLY on Arduino (ATMEGA2560). I have created a near-identical copy compatible with C++11 and the code works FLAWLESSLY.

I will describe in another comment my test setup to confirm that it only fails on the Arduino-based board.

To give you a brief preview, here is another screenshot of my serial console:

where the Vector filesCreated is exclusively used inside the main .cpp source file while the Vector filesInCard is passed by reference to a function. Inside it, the values are correctly retrieved and printed, HOWEVER, once the code goes back to the main source, the Vector is EMPTY.

Any thoughts?