Compare memcpy to string literal? C
Multi tool use
-1
net_buffer_t netBuffer = nb_create(fd, MAX_LINE_LENGTH);
char byteArray[MAX_LINE_LENGTH] = "";
char commandString[COMMAND_LENGTH] = "";
nb_read_line(netBuffer, byteArray);
memcpy(commandString, byteArray, COMMAND_LENGTH);
commandString[COMMAND_LENGTH] = '';
printf("%dn", strcmp(commandString, "HELO"));
if(strcmp(commandString, "HELO") == 0){
printf("%sn", "got HELO!");
}else if(strcmp(commandString, "MAIL") == 0){
printf("%sn", "You got mail");
}else if(strcmp(commandString, "RCPT") == 0){
}else if(strcmp(commandString, "DATA") == 0){
}else if(strcmp(commandString, "NOOP") == 0){
}else if(strcmp(commandString, "QUIT") == 0){
}
So what my code does is it's supposed to read from a stream then compare it, but for some reason when I type in "HELO" and printf("%sn", commandString) it prints out "HELO" as well but I get 10 from the strcmp print line.
c memcpy strcmp
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
add a comment |
-1
net_buffer_t netBuffer = nb_create(fd, MAX_LINE_LENGTH);
char byteArray[MAX_LINE_LENGTH] = "";
char commandString[COMMAND_LENGTH] = "";
nb_read_line(netBuffer, byteArray);
memcpy(commandString, byteArray, COMMAND_LENGTH);
commandString[COMMAND_LENGTH] = '';
printf("%dn", strcmp(commandString, "HELO"));
if(strcmp(commandString, "HELO") == 0){
printf("%sn", "got HELO!");
}else if(strcmp(commandString, "MAIL") == 0){
printf("%sn", "You got mail");
}else if(strcmp(commandString, "RCPT") == 0){
}else if(strcmp(commandString, "DATA") == 0){
}else if(strcmp(commandString, "NOOP") == 0){
}else if(strcmp(commandString, "QUIT") == 0){
}
So what my code does is it's supposed to read from a stream then compare it, but for some reason when I type in "HELO" and printf("%sn", commandString) it prints out "HELO" as well but I get 10 from the strcmp print line.
c memcpy strcmp
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
You're writing to an out of bounds index in commandString, btw. And what isnb_read_line()?
– Shawn
Nov 22 '18 at 22:10
The problem may also be innb_read_linewhich you didn't post….
– Jabberwocky
Nov 22 '18 at 22:11
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19
add a comment |
-1
-1
-1
net_buffer_t netBuffer = nb_create(fd, MAX_LINE_LENGTH);
char byteArray[MAX_LINE_LENGTH] = "";
char commandString[COMMAND_LENGTH] = "";
nb_read_line(netBuffer, byteArray);
memcpy(commandString, byteArray, COMMAND_LENGTH);
commandString[COMMAND_LENGTH] = '';
printf("%dn", strcmp(commandString, "HELO"));
if(strcmp(commandString, "HELO") == 0){
printf("%sn", "got HELO!");
}else if(strcmp(commandString, "MAIL") == 0){
printf("%sn", "You got mail");
}else if(strcmp(commandString, "RCPT") == 0){
}else if(strcmp(commandString, "DATA") == 0){
}else if(strcmp(commandString, "NOOP") == 0){
}else if(strcmp(commandString, "QUIT") == 0){
}
So what my code does is it's supposed to read from a stream then compare it, but for some reason when I type in "HELO" and printf("%sn", commandString) it prints out "HELO" as well but I get 10 from the strcmp print line.
c memcpy strcmp
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
net_buffer_t netBuffer = nb_create(fd, MAX_LINE_LENGTH);
char byteArray[MAX_LINE_LENGTH] = "";
char commandString[COMMAND_LENGTH] = "";
nb_read_line(netBuffer, byteArray);
memcpy(commandString, byteArray, COMMAND_LENGTH);
commandString[COMMAND_LENGTH] = '';
printf("%dn", strcmp(commandString, "HELO"));
if(strcmp(commandString, "HELO") == 0){
printf("%sn", "got HELO!");
}else if(strcmp(commandString, "MAIL") == 0){
printf("%sn", "You got mail");
}else if(strcmp(commandString, "RCPT") == 0){
}else if(strcmp(commandString, "DATA") == 0){
}else if(strcmp(commandString, "NOOP") == 0){
}else if(strcmp(commandString, "QUIT") == 0){
}
So what my code does is it's supposed to read from a stream then compare it, but for some reason when I type in "HELO" and printf("%sn", commandString) it prints out "HELO" as well but I get 10 from the strcmp print line.
c memcpy strcmp
c memcpy strcmp
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
asked Nov 22 '18 at 22:03
DolanTheMFWizardDolanTheMFWizard
938
938
You're writing to an out of bounds index in commandString, btw. And what isnb_read_line()?
– Shawn
Nov 22 '18 at 22:10
The problem may also be innb_read_linewhich you didn't post….
– Jabberwocky
Nov 22 '18 at 22:11
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19
add a comment |
You're writing to an out of bounds index in commandString, btw. And what isnb_read_line()?
– Shawn
Nov 22 '18 at 22:10
The problem may also be innb_read_linewhich you didn't post….
– Jabberwocky
Nov 22 '18 at 22:11
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19
You're writing to an out of bounds index in commandString, btw. And what is
nb_read_line()?– Shawn
Nov 22 '18 at 22:10
You're writing to an out of bounds index in commandString, btw. And what is
nb_read_line()?– Shawn
Nov 22 '18 at 22:10
The problem may also be in
nb_read_line which you didn't post….– Jabberwocky
Nov 22 '18 at 22:11
The problem may also be in
nb_read_line which you didn't post….– Jabberwocky
Nov 22 '18 at 22:11
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19
add a comment |
1 Answer
1
active
oldest
votes
1
char commandString[COMMAND_LENGTH] = "";
...
commandString[COMMAND_LENGTH] = '';
You are writing past the end of the commandString array, because C arrays use zero-based indices. You should allocate an extra element for the null termination character.
char commandString[COMMAND_LENGTH + 1];
// no need to initialize if you are overwriting anyway
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
1
strncpy()has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).
– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
add a comment |
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1 Answer
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1 Answer
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char commandString[COMMAND_LENGTH] = "";
...
commandString[COMMAND_LENGTH] = '';
You are writing past the end of the commandString array, because C arrays use zero-based indices. You should allocate an extra element for the null termination character.
char commandString[COMMAND_LENGTH + 1];
// no need to initialize if you are overwriting anyway
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
1
strncpy()has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).
– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
add a comment |
1
char commandString[COMMAND_LENGTH] = "";
...
commandString[COMMAND_LENGTH] = '';
You are writing past the end of the commandString array, because C arrays use zero-based indices. You should allocate an extra element for the null termination character.
char commandString[COMMAND_LENGTH + 1];
// no need to initialize if you are overwriting anyway
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
1
strncpy()has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).
– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
add a comment |
1
1
1
char commandString[COMMAND_LENGTH] = "";
...
commandString[COMMAND_LENGTH] = '';
You are writing past the end of the commandString array, because C arrays use zero-based indices. You should allocate an extra element for the null termination character.
char commandString[COMMAND_LENGTH + 1];
// no need to initialize if you are overwriting anyway
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
char commandString[COMMAND_LENGTH] = "";
...
commandString[COMMAND_LENGTH] = '';
You are writing past the end of the commandString array, because C arrays use zero-based indices. You should allocate an extra element for the null termination character.
char commandString[COMMAND_LENGTH + 1];
// no need to initialize if you are overwriting anyway
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
edited Nov 22 '18 at 22:32
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
answered Nov 22 '18 at 22:09
meowgoesthedogmeowgoesthedog
9,51431426
9,51431426
1
strncpy()has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).
– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
add a comment |
1
strncpy()has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).
– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
1
1
strncpy() has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).– Shawn
Nov 22 '18 at 22:23
strncpy() has too many peculiarities to make it a good suggestion (including that it might not add a trailing nul to the destination depending on the length of the source string).– Shawn
Nov 22 '18 at 22:23
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
@Shawn wow didn't know that, always thought it wrote the null character regardless. Thanks for the heads-up
– meowgoesthedog
Nov 22 '18 at 22:32
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
It's a tricky function prone to biting folks who didn't read the fine print before using it (which is most people). Personally, I wish it wasn't in the standard.
– Shawn
Nov 22 '18 at 22:49
add a comment |
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7DIohGC,hJF8
You're writing to an out of bounds index in commandString, btw. And what is
nb_read_line()?– Shawn
Nov 22 '18 at 22:10
The problem may also be in
nb_read_linewhich you didn't post….– Jabberwocky
Nov 22 '18 at 22:11
The only thing that is obvious about nb_read_line() is that it does not provide you with a properly zero-terminated C string. Trying to turn it into one did not help. The printf statement doesn't really prove anything, it might well spit out unprintable control characters. Look at the docs or definition of nb_read_line, some odds that it returns the number of bytes that were read. That tells you where to put the 0.
– Hans Passant
Nov 22 '18 at 23:32
turned out to be the out of range null value
– DolanTheMFWizard
Nov 23 '18 at 2:19