Avoid floats in for loops¶
ID: cpp/loop-variable-float
Kind: problem
Security severity:
Severity: recommendation
Precision: high
Tags:
- correctness
- reliability
- external/jsf
Query suites:
- cpp-security-and-quality.qls
Click to see the query in the CodeQL repository
This rule finds float variables being used as loop counter. float values are prone to rounding and truncation. In particular, very large and very small float values are prone to rounding errors and could lead to unexpected loop behavior.
Recommendation¶
Use an integral variable instead of a float variable for the loop counter.
Example¶
void f() {
float i = 0.0f;
//wrong: float used as loop counter
for (i = 0; i < 1000000.0f; i++) { //may execute 1000000 +x/-x times
//...
}
for (i = 0; i < 100000000.0f; i++) { //may never terminate, as rounding errors
//cancel out the addition of 1.0 once
//i becomes large enough
//...
}
}
References¶
AV Rule 197, Joint Strike Fighter Air Vehicle C++ Coding Standards. Lockheed Martin Corporation, 2005.
MISRA C++ Rule 6-5-1, Guidelines for the use of the C++ language in critical systems. The Motor Industry Software Reliability Associate, 2008.
FLP30-C. Do not use floating-point variables as loop counters