tesseract APIs with OpenMp: sometimes segmentation faults, sometimes not - c++

Question

I'm writing a small demo with tesseract APIs to run in parallel via OpenMp; it is basically an example taken from tesseract APIs usage page, with some openmp flavour added on it.
The executable takes two arguments: a tif file and an integer for the page to be ocrized.
I'm compiling like this:
clang-omp++ -o tessapi-quality tessapi-quality.cpp -<TESSERACT_FLAGS> -O3 -fopenmp -g.
The problem I'm facing is that it works most of the time, but one over five - more or less - it throws a seg fault.
I tried and debug with gdb, but couldn't find out, 'cause it dies sometimes on a tesseract baseapi function, sometimes on another.
Unfortunately I cannot install valgrind on the machine where I'm working on now.
I'm aware that it's not handy to be tested from anyone who has not tesseract installed, but maybe I'm missing something big in the code and you can help me just taking a look.
This is the code:
#include <stdlib.h>
#include <iostream>
#include <leptonica/allheaders.h>
#include <omp.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <tesseract/api/baseapi.h>
void getCompImage(const char* filename, int page){
Pix* image;
Pixa** pixa;
int** blockids;
image = pixReadTiff(filename, page);
int num_threads = 4;
omp_set_num_threads(num_threads);
#pragma omp parallel
{
tesseract::TessBaseAPI *papi = new tesseract::TessBaseAPI();
if (papi->Init(NULL, "eng")) {
#pragma omp critical
{
std::cout << "Could not initialize tesseract " << '\n';
}
exit(1);
}
papi->SetImage(image);
Boxa* boxes = papi->GetComponentImages(tesseract::RIL_TEXTLINE, true, pixa, blockids);
#pragma omp barrier
#pragma omp for schedule(static)
for (int i = 0; i < boxes->n; i++) {
BOX* box = boxaGetBox(boxes, i, L_CLONE);
papi->SetRectangle(box->x, box->y, box->w, box->h);
char* ocrResult = papi->GetUTF8Text();
int my_thread = omp_get_thread_num();
#pragma omp critical
{
std::cout << "Thread: " << my_thread << " Page: " << page << " Box[" << i << "] text: " << ocrResult << "\n";
}
}
// Destroy used object and release memory
papi->End();
}
pixDestroy(&image);
}
int main(int argc, char *argv[])
{
if (argc != 3){
printf("Type the (tiff) file name to OCRize\n"
"Then the page in the file to OCRize (first page=0, second=1 etc..)\n\n");
exit(-1);
}
int page = atoi(argv[2]);
getCompImage(argv[1], page);
return 0;
}