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strstream Memory Leak

P: n/a
I am working on a c++ module, where large amount of data needs to be
written to a stream and str() method is been used to assign the value
of this to the char*. This produces the intended result. But when i run
purify on it i get the following results.

[W] MLK: Memory leak of 8656 bytes from 9 blocks allocated in
strstreambuf::doallocate(void) [Builder.exe]
Distribution of leaked blocks
987 bytes from 1 block of 987 bytes (0x03977ea8)
980 bytes from 1 block of 980 bytes (0x038ff010)
976 bytes from 1 block of 976 bytes (0x03974cf8)
969 bytes from 1 block of 969 bytes (0x03969290)
962 bytes from 1 block of 962 bytes (0x03967a00)
960 bytes from 1 block of 960 bytes (0x03965d78)
958 bytes from 1 block of 958 bytes (0x038fe388)
957 bytes from 1 block of 957 bytes (0x003961f8)
907 bytes from 1 block of 907 bytes (0x041080b0)
Allocation location
new(UINT,int,char const*,int) [dbgnew.cpp:46]
strstreambuf::doallocate(void) [_strstre.cpp:201]
strstreambuf::overflow(int) [_strstre.cpp:256]
streambuf::xsputn(char const*,int) [streamb.cpp:182]
streambuf::sputn(char const*,int) [.\.\streamb.h:187]
ostream::writepad(char const*,char const*)
[ostream.cpp:166]
ostream::<<(char const*) [ostream.cpp:61]
writeInvisibleObject(char *,char *,char *,char const*)
[E:\Builder\src\main.cpp:2499]

This happens at the line where the char* is been assigned to the
strstream variable.

strstream strmvar;
strmvar << dataChar;

char* datadetail = strmvar.str();
delete datadetail;

Initially i assumed the reason to be writing a char* to the strstream
variable. But the error occured when i tried with int even. The purify
results indicate that it if beacuse of a overflow to the strstream var.
As for as my understanding the new memory that is been allocated was
never deleted. Since the program involves a huge amount of data this
could occur. Is the overflow the cause for the leak? Is there a way to
get rid of this leak? I definitely need to remove this as we are
running the code in batch mode for a set of input files. and this may
affect the performance of the application when run continously and may
lead to out of memory error even.

Can someone help me?

Oct 17 '06 #1
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5 Replies


P: n/a
ni******@gmail.com wrote:
I am working on a c++ module, where large amount of data needs to be
written to a stream and str() method is been used to assign the value
of this to the char*. This produces the intended result. But when i run
purify on it i get the following results.

[W] MLK: Memory leak of 8656 bytes from 9 blocks allocated in
strstreambuf::doallocate(void) [Builder.exe]
Distribution of leaked blocks
987 bytes from 1 block of 987 bytes (0x03977ea8)
980 bytes from 1 block of 980 bytes (0x038ff010)
976 bytes from 1 block of 976 bytes (0x03974cf8)
969 bytes from 1 block of 969 bytes (0x03969290)
962 bytes from 1 block of 962 bytes (0x03967a00)
960 bytes from 1 block of 960 bytes (0x03965d78)
958 bytes from 1 block of 958 bytes (0x038fe388)
957 bytes from 1 block of 957 bytes (0x003961f8)
907 bytes from 1 block of 907 bytes (0x041080b0)
Allocation location
new(UINT,int,char const*,int) [dbgnew.cpp:46]
strstreambuf::doallocate(void) [_strstre.cpp:201]
strstreambuf::overflow(int) [_strstre.cpp:256]
streambuf::xsputn(char const*,int) [streamb.cpp:182]
streambuf::sputn(char const*,int) [.\.\streamb.h:187]
ostream::writepad(char const*,char const*)
[ostream.cpp:166]
ostream::<<(char const*) [ostream.cpp:61]
writeInvisibleObject(char *,char *,char *,char const*)
[E:\Builder\src\main.cpp:2499]

This happens at the line where the char* is been assigned to the
strstream variable.

strstream strmvar;
strmvar << dataChar;

char* datadetail = strmvar.str();
delete datadetail;

Initially i assumed the reason to be writing a char* to the strstream
variable. But the error occured when i tried with int even. The purify
results indicate that it if beacuse of a overflow to the strstream var.
As for as my understanding the new memory that is been allocated was
never deleted. Since the program involves a huge amount of data this
could occur. Is the overflow the cause for the leak? Is there a way to
get rid of this leak? I definitely need to remove this as we are
running the code in batch mode for a set of input files. and this may
affect the performance of the application when run continously and may
lead to out of memory error even.

Can someone help me?
First, you should use std::stringstreams instead of std::strstreams if
at all possible. The latter have been deprecated.

Second, I think your problem might be that you forgot to terminate the
strstream with std::ends:

strstream strmvar;
strmvar << dataChar << ends;

Cheers! --M

Oct 17 '06 #2

P: n/a
ni******@gmail.com wrote:
>
strstream strmvar;
strmvar << dataChar;

char* datadetail = strmvar.str();
delete datadetail;
delete [] datadetail;

I'm surprised Putrify doesn't give you an explicit error on this
one.
Oct 17 '06 #3

P: n/a

Ron Natalie wrote:
ni******@gmail.com wrote:

strstream strmvar;
strmvar << dataChar;

char* datadetail = strmvar.str();
delete datadetail;

delete [] datadetail;

I'm surprised Putrify doesn't give you an explicit error on this
one.
Thanks. Since i am working on Windows probably purify didn't throw an
error on this.

I solved the problem that i had stated. That was because of the failure
to use freeze method. Once i unfreezed the buffer the destructor itself
took care of the deallocation of the strstream variable.

strmvar.rdbuf()->freeze(0);

made me fix the problem. Is this going to be a problem when I port the
application to UNIX? Do I need to make any changes to make it work?

Oct 17 '06 #4

P: n/a

mlimber wrote:
ni******@gmail.com wrote:
I am working on a c++ module, where large amount of data needs to be
written to a stream and str() method is been used to assign the value
of this to the char*. This produces the intended result. But when i run
purify on it i get the following results.

[W] MLK: Memory leak of 8656 bytes from 9 blocks allocated in
strstreambuf::doallocate(void) [Builder.exe]
Distribution of leaked blocks
987 bytes from 1 block of 987 bytes (0x03977ea8)
980 bytes from 1 block of 980 bytes (0x038ff010)
976 bytes from 1 block of 976 bytes (0x03974cf8)
969 bytes from 1 block of 969 bytes (0x03969290)
962 bytes from 1 block of 962 bytes (0x03967a00)
960 bytes from 1 block of 960 bytes (0x03965d78)
958 bytes from 1 block of 958 bytes (0x038fe388)
957 bytes from 1 block of 957 bytes (0x003961f8)
907 bytes from 1 block of 907 bytes (0x041080b0)
Allocation location
new(UINT,int,char const*,int) [dbgnew.cpp:46]
strstreambuf::doallocate(void) [_strstre.cpp:201]
strstreambuf::overflow(int) [_strstre.cpp:256]
streambuf::xsputn(char const*,int) [streamb.cpp:182]
streambuf::sputn(char const*,int) [.\.\streamb.h:187]
ostream::writepad(char const*,char const*)
[ostream.cpp:166]
ostream::<<(char const*) [ostream.cpp:61]
writeInvisibleObject(char *,char *,char *,char const*)
[E:\Builder\src\main.cpp:2499]

This happens at the line where the char* is been assigned to the
strstream variable.

strstream strmvar;
strmvar << dataChar;

char* datadetail = strmvar.str();
delete datadetail;

Initially i assumed the reason to be writing a char* to the strstream
variable. But the error occured when i tried with int even. The purify
results indicate that it if beacuse of a overflow to the strstream var.
As for as my understanding the new memory that is been allocated was
never deleted. Since the program involves a huge amount of data this
could occur. Is the overflow the cause for the leak? Is there a way to
get rid of this leak? I definitely need to remove this as we are
running the code in batch mode for a set of input files. and this may
affect the performance of the application when run continously and may
lead to out of memory error even.

Can someone help me?

First, you should use std::stringstreams instead of std::strstreams if
at all possible. The latter have been deprecated.

Second, I think your problem might be that you forgot to terminate the
strstream with std::ends:

strstream strmvar;
strmvar << dataChar << ends;

Cheers! --M
Once you are done with object of strstream that's strmvar call
freeze(true) on strmvar.
strmvar.freeze(true);
I too had the same problem earlier.
This worked fine.
But change the deprecated strstream to stringstream.

Regards
Sunil

Oct 17 '06 #5

P: n/a

ni******@gmail.com wrote:
Ron Natalie wrote:
ni******@gmail.com wrote:
>
strstream strmvar;
strmvar << dataChar;
>
char* datadetail = strmvar.str();
delete datadetail;
delete [] datadetail;

I'm surprised Putrify doesn't give you an explicit error on this
one.

Thanks. Since i am working on Windows probably purify didn't throw an
error on this.

I solved the problem that i had stated. That was because of the failure
to use freeze method. Once i unfreezed the buffer the destructor itself
took care of the deallocation of the strstream variable.

strmvar.rdbuf()->freeze(0);

made me fix the problem. Is this going to be a problem when I port the
application to UNIX? Do I need to make any changes to make it work?
As long as you are able to change things, switch to std::stringstreams
without delay, and your problems will all magically go away! (Ok,
that's an exaggeration, but it will likely help since memory management
will be much simpler.)

Cheers! --M

Oct 17 '06 #6

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