problem with sprintf_s() on win 7

User 9307625

char buffer[50] int offset =3; char Buffer[250]; sprintf_s(&buffer[offset],offset,"%s",Buffer); When we use the above funcation and application crashed with the folloing message --------------------------- Microsoft Visual C++ Debug Library --------------------------- Debug Assertion Failed! Program: xyz.exe File: f:\dd\vctools\crt_bld\self_x86\crt\src\vsprintf.c Line: 244 Expression: ("Buffer too small", 0) For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts. (Press Retry to debug the application) --------------------------- Abort Retry Ignore --------------------------- OS used : Windows 7 32bit OS Microsoft Visual Studio 2008 (VC++) Version 9.0.30729.1SP

Santhosh G_

Second parameter of sprintf_s is the size of destination buffer. If length of formatted string is greater than the size of source buffer, sprintf_s will create debug assertion. If length of string in Buffer is less than 3, then it will not create an debug assertion. Here you can change the second parameter of sprintf_s to 47,by considering offset in buffer.

CPallini

Member 9353776 wrote:

sprintf_s(&buffer[offset],offset,"%s",Buffer);

Here you are stating your destination buffer has size 3 (parameter 2 of sprintf_s (see MSDN[^]). If the source buffer (namely Buffer) contains a string with more than 3 characters then you get the assertion.

Veni, vidi, vici.

User 9307625

char buffer[50] int offset =3; char Buffer[250]; OR char buffer[50] int offset =3; char Buffer[50]; Is working fine with VS6.0, but when the same code is compiled with VS2008 I am still getting the same error as mentioned above.

User 9307625

char buffer[50] int offset =3; char Buffer[250]; OR char buffer[50] int offset =3; char Buffer[50]; Is working fine with VS6.0, but when the same code is compiled with VS2008 I am still getting the same error as mentioned above.

Santhosh G_

Which function is used in VC6.0 ? Is it sprintf() or sprintf_s() ?
If it is sprintf(), then nothing to wonder, becausee sprintfdoesnot check the output buffer size.

Santhosh G_

which function is used in VC6.0 ? Is it sprintf_s() ?
sprintf() is not checking the output buffer size. Sprintf_s ensures the output buffer overwritinng is not happening.

CPallini

Short answer: You sprintf statement is plain wrong if 'it is working fine' maybe by accident. Somewhat longer answer: If you have a 50 bytes buffer, why don't you pass 50 instead of 3? Why are you using the misleading name offset for passing a size?

Veni, vidi, vici.

Sarath C

First thing is that, trust the implementation made by Microsoft. This is a very primitive function and you will have to read the documentation first. Second you can your strcpy_s or strcat_s (if you're concatenating). sprint_s is not really a choice string copy. Third your strings must be null terminated. To understand this better, I am illustrating this with a code example

char buffer\[12\]= {0};
int offset =3;
char Buffer\[50\] = "Hello World";
sprintf\_s(buffer,sizeof(buffer),  "%s", Buffer);

in the above example buffer has 12 character in legnth and Hello World String contains 11 characters + null terminated. Anything less than 12 character size will raise assertion buffer too small. for sprintf_s only the number of characters being copied only matters. not really the original size of the buffers.

-Sarath.

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User 9307625

I have fixed the issue, I am very much thankful to all your replies