In this compliant solution, the size of the array is determined inside the block in which it is declared and passed as an argument to the function: If one does have to use memset though, then at least put all of these pointers into a nested POD struct and memset the struct. (It could still cause problems if arr is changed to a pointer rather than an array.) Most errors that I see in projects are related to the usage of this particular memset() function. Then it won't affect anything else you put in the class.
In the second case, you need to constantly review top and bottom sections to make sure you are consistent. 如果memset(a, 256, sizeof(int))和memset(a, 512, sizeof(int))的话，那么a[0]的值将是0，因为256，512的二进制最后8位全是0 2 2010-12-15 15:23:23 只看TA 引用 举报 #7 得分 0 Your message dated Mon, 08 Jul 2013 22:18:54 +0000 with message-id <[hidden email]> and subject line Bug#713722: fixed in ion 3.1.3~dfsg1-1 has caused the Debian Bug report #713722, regarding ion: FTBFS: ici/sdr/sdrxn.c:817:28: error: argument to 'sizeof' in 'memset' call is the same expression as the destination; did you mean to provide an explicit length? m...after having a long and really long thought, I have decided that memset will not be a good idea in a long run, for now I have used a After checking hundreds of C/C++ projects of various types, I can claim: memset() is the most inefficient and dangerous function.
memset(arr, 0, sizeof arr); avoids both of these problems. If we memset to zero everything from the beginning of the region, the length of the resulting C string is 0; if not to zero, then the length of the resulting C string is at least the size argument; if not from the beginning, then we've no idea, unless we knew the length before and it was less then the offset from which we started memseting.
void * memset (void * dest, int ch, std:: size_t count ); Converts the value ch to unsigned char and copies it into each of the first count characters of the object pointed to by dest .
memset(str, 0, sizeof(str)); memset(str, 0, 12); The first is wrong because sizeof(str) will always be the size of the pointer, not the size of the buffer pointed to. int a1; float a2; memset(&a1,0,sizeof(int)); memset(&a2,0,sizeof(float)); In the first case, it's easy to verify that the right sizes are being passed to memset . Compliant Solution. It sets all memory starting at a particular address (the first argument) to a particular value (the second argument) for n bytes past the starting address (n is the third argument). The Standard C library function memset( ) (in