tor/scripts/coccinelle/debugmm.cocci
Nick Mathewson 387cfccee4 Add a coccinelle script to look for {inc,dec}rements in log_debug
We want to forbid this pattern since, unlike the other log_*()
macros, log_debug() conditionally evaluates its arguments only if
debug-level logging is enabled.  Thus, a call to
    log_debug("%d", x++);
will only increment x if debugging logs are enabled, which is
probably not what the programmer intended.

One bug caused by this pattern was #30628.

This script detects log_debug( ) calls with any of E++, E--, ++E,
or --E in their arguments, where E is an arbitrary expression.

Closes ticket 30743.
2019-09-18 13:43:42 -04:00

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// Look for use of expressions with side-effects inside of debug logs.
//
// This script detects expressions like ++E, --E, E++, and E-- inside of
// calls to log_debug().
//
// The log_debug() macro exits early if debug logging is not enabled,
// potentially causing problems if its arguments have side-effects.
@@
expression E;
@@
*log_debug(... , <+... --E ...+>, ... );
@@
expression E;
@@
*log_debug(... , <+... ++E ...+>, ... );
@@
expression E;
@@
*log_debug(... , <+... E-- ...+>, ... );
@@
expression E;
@@
*log_debug(... , <+... E++ ...+>, ... );