[analyzer] Document the issue hash debugging facility

[xazax.hun]

Summary

Add documentation to the recently added issue hash dumping function.

[jklaehn]

docs/analyzer/DebugChecks.rst

247 ↗

(On Diff #121275)

typo reports?

[NoQ]

Yup, thanks!

docs/analyzer/DebugChecks.rst

255 ↗

(On Diff #121275)

Unlike printState and like all other functions, your function doesn't dump to plain stderr, but generates warnings instead. I didn't want printState to produce huge warnings because matching them with expected-warning would be more disgusting than FileChecking, but that's not your case. So i think you'd like to document it similarly to other functions, probably as // expected-warning{{'sample output'}}.

[xazax.hun]

docs/analyzer/DebugChecks.rst

255 ↗

(On Diff #121275)

Yeah, sorry for the oversight. :) I wanted to get the documentation part done as soon as possible to work on other parts. But it looks like these kinds of tasks should have the same level of attention as others.

[NoQ]

these kinds of tasks should have the same level of attention as others

Dunno really. I'm not sure anybody actually reads that doc instead of accidentally finding the checker code by debugging how the tests work.

cfe/trunk/docs/analyzer/DebugChecks.rst

- ``void clang_analyzer_printState();``
 
   Example usage::
 
     void foo() {
       int x = 1;
       clang_analyzer_printState(); // Read the stderr!
     }
 
+- ``void clang_analyzer_hashDump(int);``
+
+  The analyzer can generate a hash to identify reports. To debug what information
+  is used to calculate this hash it is possible to dump the hashed string as a
+  warning of an arbitrary expression using the function above.
+
+  Example usage::
+
+    void foo() {
+      int x = 1;
+      clang_analyzer_hashDump(x); // expected-warning{{hashed string for x}}
+    }
+
 Statistics
 ==========
 
 The debug.Stats checker collects various information about the analysis of each
 function, such as how many blocks were reached and if the analyzer timed out.
 
 There is also an additional -analyzer-stats flag, which enables various
 statistics within the analyzer engine. Note the Stats checker (which produces at
 least one bug report per function) may actually change the values reported by
 -analyzer-stats.