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Eight C++ programming mistakes the compiler won’t catch

18 points by sonic0002 15y ago

danieldk 15y ago
Three notes: 1. The SafeInt class helps detecting integer overflows: http://safeint.codeplex.com/ http://safeint.codeplex.com/ Also, most SafeInt binary operators do not allow for mixing of SafeInts for different integer types. 2. Valgrind helps with detecting use of uninitialized memory. 3. A (rather ugly) solution to prevent accidental use of = rather than == when a constant expression is used, is to make the constant expression the first operand. E.g.: if (0 = x) // fail!
- dazzawazza 15y ago
  for 3 clang will (by default report): Using the result of an assignment as a condition without parentheses Place parentheses around the assignment to silence this warning Use '==' to turn this assignment into an equality comparison this can be turned off though.
- pagekalisedown 15y ago
  3: I've rarely seen "Yoda conditions" [1] in the wild. I think it's because most compilers will output a warning when doing an assignment inside an if statement. [1] http://www.dodgycoder.net/2011/11/yoda-conditions-pokemon-exception.html http://www.dodgycoder.net/2011/11/yoda-conditions-pokemon-ex...
- wglb 15y ago
  Be sure that you have the fixed version: http://blog.regehr.org/archives/593 http://blog.regehr.org/archives/593 as there were errors in the previous.
dlsym 15y ago
Every language has its quirks... You get used to it; learn to avoid beginners mistakes; and eventually can use the language in production. C++ is not different - it can even provide you with even more interesting and unexpected ways to shoot yourself in the foot: C++ (from: http://m5p.com/~pravn/foot.html) You accidentally create a dozen instances of yourself and shoot them all in the foot. Providing emergency medical care is impossible since you can't tell which are bitwise copies and which are just pointing at others and saying, "That's me over there."
Tatyanazaxarova 15y ago
For find such errors, and many others, I recommend using static code analyzer tools. I suggest to try PVS-Studio :-) http://www.viva64.com/en/pvs-studio/ http://www.viva64.com/en/pvs-studio/
CountHackulus 15y ago
This depends entirely on which compiler you're using. Saying that these are mistakes "the compiler" won't catch is disingenuous. While VSC++2005 didn't catch these, I know that xlC on AIX will catch all of these except the integer divide "bug" at the default warning level.

18 points by sonic0002 15y ago

Three notes: 1. The SafeInt class helps detecting integer overflows: http://safeint.codeplex.com/ http://safeint.codeplex.com/ Also, most SafeInt binary operators do not allow for mixing of SafeInts for different integer types. 2. Valgrind helps with detecting use of uninitialized memory. 3. A (rather ugly) solution to prevent accidental use of = rather than == when a constant expression is used, is to make the constant expression the first operand. E.g.: if (0 = x) // fail!

dazzawazza 15y ago
for 3 clang will (by default report): Using the result of an assignment as a condition without parentheses Place parentheses around the assignment to silence this warning Use '==' to turn this assignment into an equality comparison this can be turned off though.
pagekalisedown 15y ago
3: I've rarely seen "Yoda conditions" [1] in the wild. I think it's because most compilers will output a warning when doing an assignment inside an if statement. [1] http://www.dodgycoder.net/2011/11/yoda-conditions-pokemon-exception.html http://www.dodgycoder.net/2011/11/yoda-conditions-pokemon-ex...
wglb 15y ago
Be sure that you have the fixed version: http://blog.regehr.org/archives/593 http://blog.regehr.org/archives/593 as there were errors in the previous.

dlsym 15y ago

Every language has its quirks... You get used to it; learn to avoid beginners mistakes; and eventually can use the language in production. C++ is not different - it can even provide you with even more interesting and unexpected ways to shoot yourself in the foot: C++ (from: http://m5p.com/~pravn/foot.html) You accidentally create a dozen instances of yourself and shoot them all in the foot. Providing emergency medical care is impossible since you can't tell which are bitwise copies and which are just pointing at others and saying, "That's me over there."

Tatyanazaxarova 15y ago

For find such errors, and many others, I recommend using static code analyzer tools. I suggest to try PVS-Studio :-) http://www.viva64.com/en/pvs-studio/ http://www.viva64.com/en/pvs-studio/

CountHackulus 15y ago

This depends entirely on which compiler you're using. Saying that these are mistakes "the compiler" won't catch is disingenuous. While VSC++2005 didn't catch these, I know that xlC on AIX will catch all of these except the integer divide "bug" at the default warning level.