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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.
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changes/ticket30743
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changes/ticket30743
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o Minor features (maintenance scripts):
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- Add a coccinelle script to detect bugs caused by incrementing or
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decrementing a variable inside a call to log_debug(). Since
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log_debug() is a macro whose arguments are conditionally evaluated, it
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is usually an error to do this. One such bug was 30628, in which SENDME
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cells were miscounted by a decrement operator inside a log_debug()
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call. Closes ticket 30743.
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scripts/coccinelle/debugmm.cocci
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scripts/coccinelle/debugmm.cocci
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// Look for use of expressions with side-effects inside of debug logs.
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//
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// This script detects expressions like ++E, --E, E++, and E-- inside of
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// calls to log_debug().
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//
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// The log_debug() macro exits early if debug logging is not enabled,
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// potentially causing problems if its arguments have side-effects.
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@@
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expression E;
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@@
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*log_debug(... , <+... --E ...+>, ... );
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@@
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expression E;
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@@
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*log_debug(... , <+... ++E ...+>, ... );
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expression E;
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*log_debug(... , <+... E-- ...+>, ... );
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@@
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expression E;
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@@
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*log_debug(... , <+... E++ ...+>, ... );
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