Replace sprintf with snprintf for safety

[cxzhong]

Convert all sprintf calls to snprintf with proper buffer size limits:

• Singular/dyn_modules/python/ring_wrap.cc
• Singular/dyn_modules/machinelearning/mlpredict.c
• Singular/svd_si.h
• Singular/svd/libs/amp.h
• Singular/countedref.h
• omalloc/omRet2Info.c

[cxzhong]

CC: @ederc @jankoboehm

[jankoboehm]

Thank you very much for the sprintf snprintf cleanup! Looks mostly good to me.

One point in omalloc/omRet2Info.c you might want to consider: &command[l] means to start writing at position l inside the character array command. Let n be the value returned by snprintf(...). snprintf returns the number of characters it wanted to write (even if there was not enough space). Then l += snprintf(...) can increase l past the end of command, and then the next &command[l] points outside the array. Rather write as n = snprintf(...) and only do l += n when 0 <= n < sizeof(command) - l, otherwise stop appending?

Minor thing in mlpredict.c, sizeof(B) gives the right bound only when B is an actual array; if B is a pointer it becomes pointer-size. Consider passing (buffer, length) explicitly.

[cxzhong]

Thank you very much for the sprintf snprintf cleanup! Looks mostly good to me.

One point in omalloc/omRet2Info.c you might want to consider: &command[l] means to start writing at position l inside the character array command. Let n be the value returned by snprintf(...). snprintf returns the number of characters it wanted to write (even if there was not enough space). Then l += snprintf(...) can increase l past the end of command, and then the next &command[l] points outside the array. Rather write as n = snprintf(...) and only do l += n when 0 <= n < sizeof(command) - l, otherwise stop appending?

Minor thing in mlpredict.c, sizeof(B) gives the right bound only when B is an actual array; if B is a pointer it becomes pointer-size. Consider passing (buffer, length) explicitly.

Can you review this again?

[cxzhong]

@jankoboehm This is ready for review now