can't seem to locate the struct - c

Question

I am trying to fetch values from a struct once its been updated however the problem am facing is an undeclared error as it cannot seem to see it.
sonicNav.h file
#include<stdio.h>
#include<stdlib.h>
#include"sonicThread.h"
extern void calcSonicS();
sonicThread.c file.
int funcLock = 0;
void calcSonicS() {
struct results *rData = results;
rData = malloc(sizeof(struct results));
int newVal1 = rData->sens1;
int newVal2 = rData->sens2;
int newVal3 = rData->sens3;
int newVal4 = rData->sens4;
if(funcLock == 0){
funcLock = threadFunc();//returns INT value of 1.
}
printf("value 1: %d value 2: %d value 3: %d value 4 %d\n", newVal1, newVal2, newVal3, newVal4);
}
sonicThread.h file
#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<signal.h>
#include<string.h>
#include<errno.h>
#include<pthread.h>
#include<sys/time.h>
#include<wiringPi.h>
//GPIO PINS stored within structs, for each sonic range finder.
typedef struct sonicPins{
//pins and id.
int trig;
int echo;
int id;
}args;
typedef struct results{
//all pins
int sens1;
int sens2;
int sens3;
int sens4;
}rData;
sonicThread.c file
void* setup(void *pinsPtr);
extern int threadFunc();
pthread_t pt[4];
int threadFunc()
{
struct sonicPins pinsArray[4] = { { 21, 20, 1 }, { 16, 12, 2 }, { 26, 19, 3 }, { 13, 6, 4 } };
for(int i =0; i <4; i++){
pthread_create(&pt[i], NULL, setup, &pinsArray[i] );
}
return 1;
}
void* setup(void *pinsPtr)
{
struct sonicPins *ptr = pinsPtr;
int trig = 0, Echo = 0, id;
trig = ptr->trig;
Echo = ptr->echo;
id = ptr->id;
struct results *storePtr;
}
The snippet above does update the struct "results", all threads does work concurrently each sensor giving out is own result.
Main.c
int main(){
//void(*foo1)(int, int, int);
//foo1 = &calcSonicS;
printf("In operation\n");
int operational = 1;
while(operational ==1)
{
//sonic range finders.
calcSonicS();
//gyroscope and acceometer.
}
return 0;
}
Error output:
sonicNav.c: In function ‘calcSonicS’:
sonicNav.c:5:28: error: ‘results’ undeclared (first use in this function)
sonicNav.c:5:28: note: each undeclared identifier is reported only once for each function it appears in

Answer 1

struct results *rData = results;
error: ‘results’ undeclared (first use in this function)
The above line tries to declare and define a local variable named rData, which has type struct results *, and initialise it with the value of the variable (local or global) results. The error message is telling you that there is no such variable.
What you're probably mixing up is C++ (old, bad) style initialisation:
MyClass variable = MyClass();
Since the next thing you do with rData is assigning it ...
rData = malloc(sizeof(struct results));
... the solution to your issue is to just remove that "wrong initialisation" from the preceeding line altogether. You could also pack it into a single line:
struct results *rData = malloc(sizeof(struct results));
Looking at ...
typedef struct results{
// ...
} rData;
... I'd guess that you have a serious misunderstanding of the relationship of structure (type) names, type names and variable names. The above definition gives you:
The name results as structure (type) name, so it can be used after struct to name the defined structure type.
The name rData as type name, referring to the same (structure) type as struct results.
When you then declare a variable struct results *rData you have additionally rData as name for a variable. This is possible, but far from good style.
If you remove the typedef, then things would change drastically: You'd then have a global variable named rData of type struct results.