Segmentation fault

[LL]

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;
}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s;
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // Segmentation fault
}
}

 

[Alf P. Steinbach]

* LL:

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;
}

Indicates basic lack of understanding of pointers.

Just Say No to raw pointers.

At least at this point in your learning curve.

main() {

'main' must have result type 'int', and C++ does not in general support the old
implicit 'int' of C.

float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s;
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // Segmentation fault
}
}

Solution: use std::vector for the arrays, use C++ iostreams (cout, <<) for i/o.


Cheers & hth.,

- Alf

 

[Ivan]

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;

}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s;
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // Segmentation fault
}

}

Do you know the type of fdarr_s? its float *.
So the printf statement should be:
printf("%f ", *fdarr_s);
or
printf("%p ", fdarr_s);

 

[zr]

#include <stdio.h>

float* dup(float* farr[], int n) {
  float* fdarr;
  for (int i=0; i<n; i++) {
    fdarr=*farr;
  }
  return fdarr;

}

main() {
  float *f1=new float(1.0);
  float *f2=new float(2.0);
  float *f3=new float(3.0);
  float* farr_s[]={f1,f2,f3};

  float* fdarr_s;
  fdarr_s=dup(farr_s,3);

  for (int i; i<3; i++) {
    printf("%f ", fdarr_s); // Segmentation fault
  }

}

replace:
float* fdarr;
with:
float* fdarr = new float[n];

 

[LL]

#include <stdio.h>

float* dup(float* farr[], int n) {
  float* fdarr;
  for (int i=0; i<n; i++) {
    fdarr=*farr;
  }
  return fdarr;

}

main() {
  float *f1=new float(1.0);
  float *f2=new float(2.0);
  float *f3=new float(3.0);
  float* farr_s[]={f1,f2,f3};

  float* fdarr_s;
  fdarr_s=dup(farr_s,3);

  for (int i; i<3; i++) {
    printf("%f ", fdarr_s); // Segmentation fault
  }

}

replace:
float* fdarr;
with:
float* fdarr = new float[n];

Still gives segmentation error. I made three changes.

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr=new float[n]; // Change 1
for (int i=0; i<n; i++) {
fdarr=*(farr); // Change 2
}
return fdarr;
}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s=new float[3]; // Change 3
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // should be 1.0 2.0 3.0
}
}

 

[LL]

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;
}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s;
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // Segmentation fault
}
}

The following code works. Now I need to do the same via a function.

#include <stdio.h>

main() {
float* f1=new float(1.0);
float* f2=new float(2.0);
float* f3=new float(3.0);
float* lf[]={f1,f2,f3};

printf("%f ", *(lf[1])); // 2.0
}

 

[LL]

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;
}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s;
fdarr_s=dup(farr_s,3);

for (int i; i<3; i++) {
printf("%f ", fdarr_s); // Segmentation fault
}
}

I fixed it.

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr=new float[n];
for (int i=0; i<n; i++) {
fdarr=*(farr);
}
return fdarr;
}

main() {
float *f1=new float(1.0);
float *f2=new float(2.0);
float *f3=new float(3.0);
float* farr_s[]={f1,f2,f3};

float* fdarr_s=dup(farr_s,3);

for (int i=0; i<3; i++) {
printf("%f ", fdarr_s); // 1.0 2.0 3.0
}
}

 

[Johannes Bauer]

* LL:

#include <stdio.h>

float* dup(float* farr[], int n) {
float* fdarr;
for (int i=0; i<n; i++) {
fdarr=*farr;
}
return fdarr;
}

Indicates basic lack of understanding of pointers.

Just Say No to raw pointers.

Good advice

However, I find it curious how competent people (like yourself) tend to
answer such threads in which the OP does neither care to tell what the
problem seems to be ("This code produces a segfault, but it shouldn't")
nor what his name is. Just posting code with "Segfault" as a subject is
not just rude, it borders on insolence.

Still, it made me wonder what a response might be with "Segfault" as a
subject and only

int main() { return *((int*)NULL); }

as the body

Kind regards,
Johannes