c - Segmentation fault after resizing array -


i'm trying implement algorithm, sorts words length of 100 chars alphabetically. idea each word fgets(), check if length under 100 chars , if so, put array of strings after resizing it.

now i'm getting segfault in line 37, supposed use strcpy() put string string array.

i'm pretty sure resizing of array responsible error, since segfault occurs @ 2nd word (or 2nd iteration of while-loop)

#include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h>  int cmpstr(const void* a, const void* b){     const char* aa = *(const char**)a;     const char* bb = *(const char**)b;     return strcmp(aa,bb); }  int main(int argc, char* argv[]){      //buffer array check word length     char barray[102];     char* buffer = barray;      //main array pointer     char** list;     list = (char**)calloc(1, sizeof(char*));     //if calloc fails     if(list == null){         perror("calloc() fails @ main array");         return -1;     }      //memory allocation first string     list[0] = (char*) calloc(102, sizeof(char));     if(list[0] == null){         perror("calloc() fails @ first array element");         return -1;     }      //string array index     int counter = 0;      //print flag     int flag = 0;      //create unsorted list     while(fgets(buffer, 103, stdin) != null){         //breakpoint 1         if(buffer[0] == '\n'){             break;         }         for(int = 0; < 101;i++){             //if word of legit length , not last 1             if(buffer[i] == '\n'){                 buffer[i] = '\0';                 strcpy(list[counter], buffer); //segfault @ 2nd iteration                 counter++;                 list = realloc(list, (counter + 1)  * sizeof(char*));                 list[counter] = (char*)calloc(102,sizeof(char));                 flag = 1;                 break;             }         }          if(flag==1){             flag = 0;             break;         }            //if word long         if(buffer[100] != '\0'){             printf("word long!");         }         else{             strcpy(list[counter], buffer);             counter++;         }      }      //sort list     qsort(list, counter, sizeof(char*), cmpstr);      //print list     for(int = 0; < counter; i++){         printf("%s\n", list[i]);     }      //free memory     for(int = 0; < counter; i++){         free(list[counter]);     } }

(also, feel free criticise code if see other mistakes made :) )

well yeah, looks set list = (char**)calloc(1, sizeof(char*)); means have space 1 char* in list. when try strcpy list[1] segfault.


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj...
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer ...
Read more

c# - Asp.net web api : redirect unauthorized requst to forbidden page -

im trying redirect unauthorized request forbidden page instead i'm getting forbidden page in response body , how can fix ? here's startup class : app.createperowincontext(storecontext.create); app.createperowincontext<applicationusermanager>(applicationusermanager.create); app.createperowincontext<applicationsigninmanager>(applicationsigninmanager.create); app.usecookieauthentication(new cookieauthenticationoptions { authenticationtype = defaultauthenticationtypes.applicationcookie, expiretimespan = timespan.fromdays(30), }); app.useexternalsignincookie(defaultauthenticationtypes.externalcookie); app.usetwofactorsignincookie(defaultauthenticationtypes.twofactorcookie, timespan.fromminutes(5)); app.usetwofactorrememberbrowsercookie(defaultauthenticationtypes.twofactorrememberbrowsercookie); the method im trying reach : [httpget] [authorize(roles = "admin")] public string getcurrentusername() { return userman...
Read more