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#elif condition is evaluated after a previous group was taken #709
Description
When an #if or #elif group has already been taken, simplecpp still evaluates the
conditions of later #elif directives. If one of those conditions is invalid, simplecpp
reports an error and throws away all output.
The standard says only the first group whose condition is true is processed. Later groups
are skipped, and their directives are handled as if they were in a skipped group, so their
conditions are not evaluated (C11 §6.10.1p6, C++ [cpp.cond]).
Example
#if 1
1
#elif garbage(
2
#endif
- Expected (gcc, clang): 1
- Actual (simplecpp): syntax error: failed to evaluate #elif condition, undefined function-like macro invocation: garbage( ... ) and all output is dropped.
#elif 1/0 after a taken group fails the same way, with a division-by-zero error.
Fix
Evaluate #if/#ifdef/#ifndef only inside an active group, and
#elif/#elifdef/#elifndef only when no earlier group was taken.
Side effect: #elif directives after a taken group no longer get an entry in the
ifCond list, because they aren't evaluated.
Activity
Fix cppcheck-opensource#709 Do not evaluate #elif after a taken group (…