Help with segfault - Printable Version

Code:

#include <stdio.h>

#include <assert.h>

#include <stdlib.h>

#include <string.h>



struct Person {

    char *name;

    int age;

    int height;

    int weight;

};



struct Person *Person_create(char *name, int age, int height,

        int weight)

{

    struct Person *who = malloc(sizeof(struct Person));

    assert(who != NULL);



    who->name = strdup(name);

    who->age = age;

    who->height = height;

    who->weight = weight;



    return who;

}



void Person_destroy(struct Person *who)

{

    assert(who != NULL);



    free(who->name);

    free(who);

}



void Person_print(struct Person *who)

{

    printf("Name: %s\n", who->name);

    printf("\tAge: %d\n", who->age);

    printf("\tHeight: %d\n", who->height);

    printf("\tWeight: %d\n", who->weight);

}



int main(int argc, char*argv[])

{

    //make two people structures

    struct Person *joe = Person_create("Joe Alex", 32, 64, 140);



    struct Person *frank = Person_create("Frank Blank", 20, 72, 180);



    // print them out and where they are in memory

    printf("Joe is at memory location %p:\n", joe);

    Person_print(joe);



    printf("Frank is at memory location %p:\n", frank);

    Person_print(frank);



    //make everyone age 20 years and print them again

    joe->age += 20;

    joe->height -= 2;

    joe->weight += 40;

    Person_print(joe);



    frank->age += 20;

    frank->weight += 20;

    Person_print(frank);



    //destroy them both so we clean up

    Person_destroy(joe);

    Person_destroy(frank);



    return 0;

}

Code:

$ strace ./ex16

execve("./ex16", ["./ex16"], [/* 42 vars */]) = 0

brk(NULL)                               = 0x56223f2f4000

access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)

mmap(NULL, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6c39e7c000

access("/etc/ld.so.preload", R_OK)      = 0

open("/etc/ld.so.preload", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0

close(3)                                = 0

open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=115220, ...}) = 0

mmap(NULL, 115220, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f6c39e5f000

close(3)                                = 0

access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)

open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\3\2\0\0\0\0\0"..., 832) = 832

fstat(3, {st_mode=S_IFREG|0755, st_size=1689360, ...}) = 0

mmap(NULL, 3795360, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f6c398bd000

mprotect(0x7f6c39a52000, 2097152, PROT_NONE) = 0

mmap(0x7f6c39c52000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x195000) = 0x7f6c39c52000

mmap(0x7f6c39c58000, 14752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f6c39c58000

close(3)                                = 0

mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6c39e5d000

arch_prctl(ARCH_SET_FS, 0x7f6c39e5d700) = 0

mprotect(0x7f6c39c52000, 16384, PROT_READ) = 0

mprotect(0x56223db40000, 4096, PROT_READ) = 0

mprotect(0x7f6c39e7f000, 4096, PROT_READ) = 0

munmap(0x7f6c39e5f000, 115220)          = 0

brk(NULL)                               = 0x56223f2f4000

brk(0x56223f315000)                     = 0x56223f315000

fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0

write(1, "Joe is at memory location 0x5622"..., 42Joe is at memory location 0x56223f2f4010:

) = 42

--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x3f2f4030} ---

+++ killed by SIGSEGV +++

Segmentation fault







$ gdb ex16

GNU gdb (Debian 7.12-6) 7.12.0.20161007-git

Copyright (C) 2016 Free Software Foundation, Inc.

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

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and "show warranty" for details.

This GDB was configured as "x86_64-linux-gnu".

Type "show configuration" for configuration details.

For bug reporting instructions, please see:

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For help, type "help".

Type "apropos word" to search for commands related to "word"...

Reading symbols from ex16...done.

(gdb) run

Starting program: /home/chaos/hive/projects/learn-c/lcthw/source/ex16 

Joe is at memory location 0x555555756010:



Program received signal SIGSEGV, Segmentation fault.

strlen () at ../sysdeps/x86_64/strlen.S:106

106    ../sysdeps/x86_64/strlen.S: No such file or directory.







$ valgrind ./ex16

==6234== Memcheck, a memory error detector

==6234== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.

==6234== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info

==6234== Command: ./ex16

==6234== 

Joe is at memory location 0x51d7040:

Name: Joe Alex

    Age: 32

    Height: 64

    Weight: 140

Frank is at memory location 0x51d70f0:

Name: Frank Blank

    Age: 20

    Height: 72

    Weight: 180

Name: Joe Alex

    Age: 52

    Height: 66

    Weight: 180

Name: Frank Blank

    Age: 40

    Height: 72

    Weight: 200

==6234== 

==6234== HEAP SUMMARY:

==6234==     in use at exit: 0 bytes in 0 blocks

==6234==   total heap usage: 5 allocs, 5 frees, 1,093 bytes allocated

==6234== 

==6234== All heap blocks were freed -- no leaks are possible

==6234== 

==6234== For counts of detected and suppressed errors, rerun with: -v

==6234== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)