- Q 4 Consider The Following Program Fragment Foo Int X Int Int A 10 B P I If X 3 B C Else B A Fo 1 (138.55 KiB) Viewed 42 times
absolutely no difference between an array declaration int B[] and
int *B. They are identical in all respects. • a declaration like
int A[10] allocates space in memory of size 10 words (40 bytes)
pointed to by the 4-byte pointer A • in contrast, a declaration
like int B[] just declares an uninitialized pointer B of size 4
bytes, which does not point to any memory block at all. • the
memory space for an array argument like C is assumed to be
allocated by the caller function. (3 + 2 + 2 + 2 = 9 points) (a)
What are the alias classes in the above code? Recall that alias
classes are scalar variables whose address is taken, as well as
memory-allocated variables and memory blocks. (b) Given a
flow-sensitive alias analysis, what are the alias classes that are
in the points-to set of B[] immediately after the first for loop?
(The points-to set of a pointer at a program point are the set of
all alias classes that may-alias with that pointer at that program
point.) (c) Given a flow-sensitive alias analysis, what are the
alias classes that are in the points-to set of B[] immediately
after the second for loop? (d) Given a flow-insensitive alias
analysis, what are the alias classes that are in the points-to set
of B[] immediately before the only if statement ?
Q.4 Consider the following program fragment: foo(int x, int []) { int A[10], B[], *p, i; if (x > 3) B = C else B = A; for (i=0; i<10; i++) { B = i + 3; } B = malloc (sizeof(int) * 10); for (i=0; i<10; i++) { B = A + 4; } } + Keep in mind that in the programming language: there is absolutely no difference between an array declaration int B[] and int *B. They are identical in all respects. a declaration like int A[10] allocates space in memory of size 10 words (40 bytes) pointed to by the 4-byte pointer A in contrast, a declaration like int B[] just declares an uninitialized pointer B of size 4 bytes, which does not point to any memory block at all. • the memory space for an array argument like C is assumed to be allocated by the caller function. (3 + 2 + 2 + 2 = 9 points) (a) What are the alias classes in the above code? Recall that alias classes are scalar variables whose address is taken, as well as memory-allocated variables and memory blocks. (b) Given a flow-sensitive alias analysis, what are the alias classes that are in the points-to set of B[] immediately after the first for loop? (The points-to set of a pointer at a program point are the set of all alias classes that may-alias with that pointer at that program point.) (c) Given a flow-sensitive alias analysis, what are the alias classes that are in the points-to set of B[] immediately after the second for loop? (d) Given a flow-insensitive alias analysis, what are the alias classes that are in the points-to set of B[] immediately before the only if statement ?