gdb debugging - only \n inside stdin - c

Question

I'm debugging my program in windows with GDB and need stdin.
So, I compiled it :
gcc -g abstieg2.c
gdb a
break 1
run < graph1.in
But the stdin has only \n in it!
do{
getline(&line,&size,stdin);
} while(!strcmp("\n",line)); // for testing, gets stuck forever, but only with gdb
I really can't see what more can be relevant to this problem.
Thanks
stripped down version of my code:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <limits.h>
void *errorchecked_malloc(unsigned int);
unsigned int correctinput(char**);
void free_us();
void my_qsort(int , int r);
unsigned int *Dijkstra(int , int , unsigned int , int );
unsigned int min_distance(unsigned int* , int );
int linearsearch(int);
char* strerror(int);
unsigned int *start_edge=NULL; // Input of edges is organised into three array
unsigned int *end_edge=NULL;
unsigned int *length_edge=NULL;
unsigned int *base_camp=NULL ; // Input of basecamps
unsigned int *Dijkstra_dist=NULL; // distance value of dijkstra algorithm
unsigned int *Dijkstra_vis=NULL; // visited by dijkstra algorithm?
unsigned int *Dijkstra_predec=NULL ; // predecessor of dijkstra algorithm
unsigned int* found=NULL;
int * pos_in_vertices;
char* store_for_reset= NULL; // line (input) char* wil be changed, in store_for_reset line will be saved
int basecamp_length=0;
/*Aim: Find the shortest way in a graph from start_vertices to finish_vertices
* restrictions:
* -2 Day travel with max_distance per day
* -after one day a basecamp must be reached( or the finish vertices)
* -N vertices <=N
*
* Input is organized as following:
* start_vertices finish_vertices d_max\n //
* start_vertices end_vertices max_distance\n // for each edge
* ...
* base_camp\n
* base_camp\n
* ...
*/
int main( ) {
int N=0; // count of vertices
int arg_line_count=0; //
unsigned int start; // First three Input of start basecamp
unsigned int end; // finish basecamp
unsigned int d_max; // maximum travel distance per day
char* line = (char *)errorchecked_malloc(36*sizeof(char));
store_for_reset= line;
int size =strlen(line);
//Input configuration
do{
getline(&line,&size,stdin);
printf("%s",line);
} while(!strcmp("\n",line));// for testing, gets stuck forever, but only with gdb
start_edge = (int*)errorchecked_malloc(sizeof(int)*1000); // creating space, TODO dynamic space allocation
end_edge = (int*)errorchecked_malloc(sizeof(int)*1000);
length_edge = (int*)errorchecked_malloc(sizeof(int)*1000);
start = correctinput(&line); // first line input
end = correctinput(&line);
d_max = correctinput(&line);
// input of all edges
for(int i=0;fgets(line,size,stdin);i++){ // fgets returns NULL if stdin empty
printf("Zeile %d \n", i);
start_edge[i]=correctinput(&line);
printf("line: %s", line);
if(line[0]=='\0'){ // end of line, means now are only basecamps left
base_camp[0]=start_edge[i];
start_edge[i]=0;
basecamp_length=1;
break;
}
if(start_edge[i]>N) N= start_edge[i];
end_edge[i]=correctinput(&line);
length_edge[i]=correctinput(&line);
line =store_for_reset;
}
// Input of basecamps
base_camp= (int*)errorchecked_malloc(sizeof(int)*N); // generous, N is maximum of Nodes
for(int i=1;fgets(line,size,stdin);i++){
base_camp[i]=correctinput(&line);
if(line!=NULL){
printf("fatal error:Too many arguments per line while reading \"Basislagern\" input");
free_us();
exit(-1);
}
basecamp_length++;
}
free_us();
}
unsigned int correctinput( char** string){
char* test;
unsigned int tmp =strtol(*string,&test,10);
if((test[0]!=' ' && test[0]!= '\n' ) || errno != 0 ) {
printf("Don't mock me! Please use the correct input format. \n Information: ");
strerror(errno);
printf(" Next Character: \'%d\'", atoi(test));
free_us();
exit(-1);
}
//printf("test: %s, /n",test);
int i;
for(i=0;(*string)[i]>='0' && (*string)[i]<='9';i++){
*string=(*string)+ i*sizeof(char); // moves the input pointer to the next argument( therefore pointer to pointer)
}
if(*string[i]==' ')string++;
return tmp;
}
void free_us(){
free(start_edge);
free(end_edge);
free(length_edge);
free(base_camp);
free(Dijkstra_dist);
free(Dijkstra_vis);
free(pos_in_vertices);
free(Dijkstra_predec);
free(store_for_reset);
free(found);
}
void *errorchecked_malloc(unsigned int size){
void *ptr;
ptr = malloc(size);
if(ptr == NULL) {
fprintf(stderr, "Error: could not allocate heap memory. \n");
free_us();
exit(-1);
}
return ptr;
}
Input looks like this:
0 1 3924456639
0 5 1268156980
0 18 293858388
0 74 142402607
1 4 145988610
....
24
1
27
79
4
70
...

Answer 1

You are probably hitting this Windows specific gdb bug:
https://www.cygwin.com/ml/cygwin/1999-04/msg00308.html
Try to upgrade to a latest version of gdb (8.0 as of now).
Among other things there were some enhancements for debugging on MS-Windows in this release. See in NEWS file:
55 * Native debugging on MS-Windows supports command-line redirection
56
57 Command-line arguments used for starting programs on MS-Windows can
58 now include redirection symbols supported by native Windows shells,
59 such as '<', '>', '>>', '2>&1', etc. This affects GDB commands such
60 as "run", "start", and "set args", as well as the corresponding MI
61 features.