Gotcha (programming)
In programming, a gotcha is a valid construct in a system, program or programming language that works as documented but is counter-intuitive and almost invites mistakes because it is both easy to invoke and unexpected or unreasonable in its outcome.[1]
Example[]
The classic gotcha in C/C++ is the construct
if (a = b) code;
It is syntactically valid: it puts the value of b
into a
and then executes code
if a
is non-zero. Sometimes this is even intended. However most commonly it is a typo: the programmer probably meant
if (a == b) code;
which executes code
if a
and b
are equal.[1] Modern compilers will usually generate a warning when encountering the former construct (conditional branch on assignment, not comparison), depending on compiler options (e.g., -Wall option for gcc). To avoid this gotcha, there is a recommendation[2] to keep the constants in the left side of the comparison, e.g. 42 == x
rather than x == 42
. This way, using =
instead of ==
will cause a compiler error (see yoda conditions). Many kinds of gotchas are not detected by compilers, however.[citation needed]
See also[]
References[]
Further reading[]
- Stephen C. Dewhurst (2003). C++ Gotchas (Avoiding Common Problems in Coding and Design). Addison-Wesley. ISBN 0321125185.
External links[]
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Look up gotcha in Wiktionary, the free dictionary. |
- C Traps and Pitfalls by Andrew Koenig
- C++ Gotchas A programmer's guide to avoiding and correcting ninety-nine of the most common, destructive, and interesting C++ design and programming errors, by Stephen C. Dewhurst
- Computer programming folklore
- Programming language folklore