CODEWITHSUNDEEP
cbittwos-complement
Aaron Swartz
Aaron Swartz

Reputation: 3

datalab of CSAPP(isTmax):! seems unoperative

my thought is just like this question. i code isTmax like this:

int isTmax(int x) {
  return  !((~x)+(~x)); // it should be right, the operator "!" seem to not work
}

x is 2s complement, 32-bit representations of integers when i use btest to test function, it generate as follows:

ERROR: Test isTmax(2147483647[0x7fffffff]) failed... ...Gives 0[0x0]. Should be 1[0x1]

my question is: why 0? it seems like ! not work.

additionally, i get warning when running btest:

btest.c: In function ‘test_function’: btest.c:334:23: warning: ‘arg_test_range’ may be used uninitialized [-Wmaybe-uninitialized] 334 | if (arg_test_range[2] < 1) | ~~~~~~~~~~~~~~^~~ btest.c:299:9: note: ‘arg_test_range’ declared here 299 | int arg_test_range[3]; /* test range for each argument */ | ^~~~~~~~~~~~~~

maybe there is something wrong with my lab environment?

Upvotes: -1

Views: 409

Answers (1)

zixiangcode
zixiangcode

Reputation: 9

This is only a warning message and does not affect your test. You can use -w in the makefile to ignore this warning

Upvotes: -1

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