i#4139: Add method to clear droption values for static re-attach (#5335)

The values of droption accumulated options are not reset on detach,
causing them to accumulate in a statically-linked client.

There is no control point for droption to do this automatically, so we
add droption_parser_t::clear_values() that a client can call.

Adds a call to clear_values() in drmemtrace.

Augments the drmemtrace burst_malloc test to fail when the options are
not reset (i.e., fail without this fix).  This serves as a test of the
new feature, as the existing droption tests do not have static clients
nor simple ways to add re-attaches.

Adds a section to the droption documentation explaining the new
feature.

Fixes #4139

api/docs/release.dox

@@ -136,6 +136,8 @@ Further non-compatibility-affecting changes include:
  - Added alias support to droption.
  - The drcpusim option -blacklist was renamed to -blocklist but the old name
    is still accepted.
+ - Added droption_parser_t::clear_values() for re-setting accumulating option
+   values on re-attach for statically linked clients.
 
 The changes between version 9.0.0 and 8.0.0 include the following compatibility
 changes:

clients/drcachesim/tests/burst_malloc.cpp

@@ -1,5 +1,5 @@
 /* **********************************************************
- * Copyright (c) 2016-2020 Google, Inc.  All rights reserved.
+ * Copyright (c) 2016-2022 Google, Inc.  All rights reserved.
  * **********************************************************/
 
 /*
@@ -157,6 +157,7 @@ main(int argc, const char *argv[])
                    // Test aliases with differing arg counts.
                    " -record_function \"has_aliases|2&alias_1arg|1&alias_3args|3\""
 #endif
+                   // Deliberately test a duplication warning on "malloc".
                    // Test large values that require two entries.
                    " -record_function \"malloc|1&return_big_value|1\"'"))
         std::cerr << "failed to set env var!\n";

clients/drcachesim/tests/offline-burst_malloc.templatex

@@ -1,6 +1,21 @@
 pre-DR init
-Warning: duplicated function name .*
+Warning: duplicated function name malloc in [^W]*
+pre-DR start
+pre-DR detach
+DynamoRIO statistics:
+ *Peak threads under DynamoRIO control : *1
 .*
+all done
+pre-DR init
+Warning: duplicated function name malloc in [^W]*
+pre-DR start
+pre-DR detach
+DynamoRIO statistics:
+ *Peak threads under DynamoRIO control : *1
+.*
+all done
+pre-DR init
+Warning: duplicated function name malloc in [^W]*
 pre-DR start
 pre-DR detach
 DynamoRIO statistics:

clients/drcachesim/tests/offline-burst_reattach.templatex

@@ -1,6 +1,4 @@
 pre-DR init
-Warning: duplicated function name .*
-.*
 pre-DR start
 pre-DR detach
 .*

clients/drcachesim/tracer/tracer.cpp

@@ -1,5 +1,5 @@
 /* ******************************************************************************
- * Copyright (c) 2011-2021 Google, Inc.  All rights reserved.
+ * Copyright (c) 2011-2022 Google, Inc.  All rights reserved.
  * Copyright (c) 2010 Massachusetts Institute of Technology  All rights reserved.
  * ******************************************************************************/
 
@@ -2000,6 +2000,8 @@ event_exit(void)
     drmgr_exit();
     func_trace_exit();
     drx_exit();
+    /* Avoid accumulation of option values on static-link re-attach. */
+    droption_parser_t::clear_values();
 }
 
 static bool

ext/droption/droption.dox

@@ -43,6 +43,7 @@ declaration and parsing for both clients and standalone programs.
  - \ref sec_droption_types
  - \ref sec_droption_html
  - \ref sec_droption_aliases
+ - \ref sec_droption_reattach
 
 \section sec_droption_setup Setup
 
@@ -190,4 +191,12 @@ droption_t<std::string> op_blocklist(
     "should not be reported.");
 \endcode
 
+\section sec_droption_reattach Clearing Accumulated Values on Re-attach
+
+For options that accumulate values (#DROPTION_FLAG_ACCUMULATE), a
+re-attach with a statically linked client will keep the old value from
+the prior attach.  The `droption_parser_t::clear_values()` function
+can be called from the client on exit or initialization to clear all
+the values.
+
 */

ext/droption/droption.h

@@ -342,6 +342,22 @@ class droption_parser_t {
         return names_[0];
     }
 
+    /**
+     * For clients statically linked into the target application, global state is not
+     * reset between a detach and re-attach.  Thus, #DROPTION_FLAG_ACCUMULATE options
+     * will append to their values from the prior run.  This function is provided for
+     * a client to call on detach or re-attach to reset these values.
+     */
+    static void
+    clear_values()
+    {
+        for (std::vector<droption_parser_t *>::iterator opi = allops().begin();
+             opi != allops().end(); ++opi) {
+            droption_parser_t *op = *opi;
+            op->clear_value();
+        }
+    }
+
 protected:
     virtual bool
     option_takes_arg() const = 0;
@@ -357,6 +373,8 @@ class droption_parser_t {
     clamp_value() = 0;
     virtual std::string
     default_as_string() const = 0;
+    virtual void
+    clear_value() = 0;
 
     // To avoid static initializer ordering problems we use a function:
     static std::vector<droption_parser_t *> &
@@ -512,6 +530,14 @@ template <typename T> class droption_t : public droption_parser_t {
         return value_;
     }
 
+    /** Resets the value of this option to the default value. */
+    void
+    clear_value() override
+    {
+        value_ = defval_;
+        is_specified_ = false;
+    }
+
     /** Returns the separator of the option value
      * (see #DROPTION_FLAG_ACCUMULATE).
      */