Anfang cpp Entwickler EXC_BAD_ACCES Fehler beim Laden der Instanz

Question

Kürzlich begann ich C++ zu lernen. Ich bin es gewohnt, in Objective-C zu programmieren, also mache ich vielleicht ein paar Dinge falsch. Ich habe eine Niederschrift der gdb Sitzung gemacht:

Script started on Sat Jan 15 17:47:24 2011 
bash-3.2$ gdb sscm 
GNU gdb 6.3.50-20050815 (Apple version gdb-1510) (Wed Sep 22 02:45:02 UTC 2010) 
Copyright 2004 Free Software Foundation, Inc. 
GDB is free software, covered by the GNU General Public License, and you are 
welcome to change it and/or distribute copies of it under certain conditions. 
Type "show copying" to see the conditions. 
There is absolutely no warranty for GDB. Type "show warranty" for details. 
This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries ... done 

(gdb) break ServerOptions::ServerOptions 
[0] cancel 
[1] all 
[2] ServerOptions::ServerOptions(int, char const**) at ServerOptions.cpp:33 
[3] ServerOptions::ServerOptions(int, char const**) at ServerOptions.cpp:33 
> 3 
Breakpoint 1 at 0x7595: file ServerOptions.cpp, line 33. 
(gdb) list 
9 
10 #include <iostream> 
11 
12 #include "Logger.h" 
13 #include "ServerOptions.h" 
14 
15 
16 int main(int argc, const char **argv) { 
17 using namespace std; 
18 ServerOptions options(argc, argv); 
(gdb) run 
Starting program: /Users/ief2/Desktop/SSCM-1.0.0.9/server/sscmd 
Reading symbols for shared libraries ++. done 

Breakpoint 1, ServerOptions::ServerOptions (this=0xbffff7a8, argc=1, argv=0xbffff7f0) at ServerOptions.cpp:33 
33 ServerOptions::ServerOptions(int argc, const char **argv) 
(gdb) s 
36 bool noErrorsEncountered = true; 
(gdb) list 
31 is a fatal error. 
32 */ 
33 ServerOptions::ServerOptions(int argc, const char **argv) 
34 { 
35 /* setup default values */ 
36 bool noErrorsEncountered = true; 
37 int isDaemon = true; 
38 int displayHelp = false; 
39 int port = DEFAULT_BIND_PORT; 
40 std::string rootFolder = ""; 
(gdb) s 
37 int isDaemon = true; 
(gdb) s 
38 int displayHelp = false; 
(gdb) s 
39 int port = DEFAULT_BIND_PORT; 
(gdb) 
40 std::string rootFolder = ""; 
(gdb) list 
35 /* setup default values */ 
36 bool noErrorsEncountered = true; 
37 int isDaemon = true; 
38 int displayHelp = false; 
39 int port = DEFAULT_BIND_PORT; 
40 std::string rootFolder = ""; 
41 int isSilent = 0; 
42 
43 Logger logger = Logger::sharedLogger(); 
44 
(gdb) 
45 /* Process the configuration file */ 
46 { 
47 int status; 
48 std::string anArgument; 
49 KeyFile file(DEFAULT_CONFIGURATION_FILE, 
50  &status); 
51 
52 if(status != 0 && status != ENOENT) { 
53 std::stringstream strstr; 
54 strstr << 
(gdb) lists[Klists[K 
41 int isSilent = 0; 
(gdb) 
43 Logger logger = Logger::sharedLogger(); 
(gdb) 
Logger::sharedLogger() at Logger.cpp:28 
28 if(logger == NULL) { 
(gdb) list 
23 } 
24 
25 Logger& Logger::sharedLogger(void) { 
26 static Logger *logger = NULL; 
27 
28 if(logger == NULL) { 
29 new Logger(""); 
30 } 
31 
32 return *logger; 
(gdb) s 
29 new Logger(""); 
(gdb) 
Logger::Logger (this=0x100160, fullPath=@0xbffff568) at Logger.cpp:16 
16 Logger::Logger(std::string fullPath) { 
(gdb) list 
11 
12 #pragma mark - 
13 #pragma mark Public Implementation 
14 
15 #pragma mark Constructors and Destructors 
16 Logger::Logger(std::string fullPath) { 
17 _filename = fullPath; 
18 _isSilent = false; 
19 } 
20 
(gdb) s 
17 _filename = fullPath; 
(gdb) 
18 _isSilent = false; 
(gdb) 
19 } 
(gdb) 
Logger::sharedLogger() at Logger.cpp:32 
32 return *logger; 
(gdb) 
33 } 
(gdb) 
Logger::Logger (this=0xbffff6ec) at Logger.h:21 
21 class Logger { 
(gdb) llist ist 
16 #include <cerrno> 
17 #include <cstring> 
18 
19 #pragma mark - 
20 #pragma mark Private Interface 
21 class Logger { 
22 private: 
23 std::string _filename; 
24 bool _isSilent; 
25 
(gdb) 
26 public: 
27 #pragma mark Constructors and Destructors 
28 Logger(std::string fullPath); 
29 ~Logger(void); 
30 static Logger& sharedLogger(void); 
31 
32 #pragma mark Getters and Setters 
33 std::string getFilename(void) const; 
34 void setFilename(std::string newF); 
35 
(gdb) s 

Program received signal EXC_BAD_ACCESS, Could not access memory. 
Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 
0x980f7b33 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string() 
(gdb) ki 
Kill the program being debugged? (y or n) y 
(gdb) q 
bash-3.2$ exit 
exit 

Script done on Sat Jan 15 17:48:59 2011 

Irgendeine Idee, warum ich diesen Fehler bekomme? Wenn Sie mehr Code benötigen, werde ich es sicherlich veröffentlichen!

Vielen Dank im Voraus, IEF2

Answer 1

Du dereferencing die NULL Zeiger auf Linie 32. In Zeile 29, ein neues Logger erstellen, aber Sie es nie zu logger zuweisen. Also, wenn Sie versuchen, es von sharedLogger, logger ist immer noch NULL, und Sie erhalten die Zugriffsverletzung. Ändern Sie Zeile 29 zu

logger = new Logger(""); 

und es sollte funktionieren.

Answer 2

Ich denke, das ist das Problem:

Logger& Logger::sharedLogger(void) { 
    static Logger *logger = NULL; 

    if(logger == NULL) { 
     new Logger(""); 
    } 

    return *logger; 
} 

Wenn Sie an den Singleton pattern streben - zuweisen, dass die neu erstellte Instanz-Adresse des statischen logger Variable, das heißt:

 logger = new Logger("");