Test program for explaining gdb's "pretty print" feature.

tests/hellopp/.gitignore

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+hellopp
+core*

tests/hellopp/LocationStruct_pp.py

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+import gdb
+
+# The PrettyPrinter object.
+class LocationPrinter:
+
+    # Save a copy of the Location.
+    def __init__(self, val):
+        self.__val = val
+
+    # Convert it to a string. gdb will call this function.
+    def to_string(self):
+        ret = ""
+
+        # Construct a python string with the values of the Location struct.
+        # It's good to handle any errors. Hence the try/catch.
+        try:
+            ret = "Location=(" + str(self.__val['city']) + "," + str(self.__val['state']) + "," + str(self.__val['zip']) + "," + str(self.__val['cell']) + ")"
+
+        except Exception as e:
+            # Any exception will be saved in the return string.
+            ret = str(e)
+
+        return ret
+
+    # A hint for gdb on the return type.
+    def display_hint (self):
+        return 'string'
+
+
+# Specify a function to detect a Location struct type and will call the PrettyPrinter object for it.
+#
+# gdb maintains a large list of PrettyPrinters for lots of data/class types. It will go through the
+# list looking for one that matches the type. If one is found, it uses it. Otherwise, gdb will
+# default to the regular way of printing data types.
+def LocationPrinter_func(val):
+    if str(val.type) == 'Location':
+        return LocationPrinter(val)
+
+# Add the function to gdb's list of PrettyPrinter functions.
+gdb.pretty_printers.append(LocationPrinter_func)
+
+

tests/hellopp/Makefile

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+.PHONY: all
+all: hellopp
+
+hellopp: hellopp.cpp
+	g++ -g -o hellopp hellopp.cpp
+
+.PHONY: clean
+clean:
+	rm -f hellopp hellopp.o
+

tests/hellopp/PersonStruct_pp.py

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+import gdb
+
+# The PrettyPrinter object.
+class PersonPrinter:
+
+    # Save a copy of the Person.
+    def __init__(self, val):
+        self.__val = val
+
+    # Convert it to a string. gdb will call this function.
+    def to_string(self):
+        ret = ""
+
+        # Construct a python string with the values of the Person struct.
+        # It's good to handle any errors. Hence the try/catch.
+        try:
+            ret = "Person=(" + str(self.__val['name']) + "," + str(self.__val['age']) + "," + str(self.__val['salary']) + "," + str(self.__val['location']) + ")"
+
+        except Exception as e:
+            # Any exception will be saved in the return string.
+            ret = str(e)
+
+        return ret
+
+    # A hint for gdb on the return type.
+    def display_hint (self):
+        return 'string'
+
+
+# Specify a function to detect a Person struct type and will call the PrettyPrinter object for it.
+#
+# gdb maintains a large list of PrettyPrinters for lots of data/class types. It will go through the
+# list looking for one that matches the type. If one is found, it uses it. Otherwise, gdb will
+# default to the regular way of printing data types.
+def PersonPrinter_func(val):
+    if str(val.type) == 'Person':
+        return PersonPrinter(val)
+
+# Add the function to gdb's list of PrettyPrinter functions.
+gdb.pretty_printers.append(PersonPrinter_func)
+
+

tests/hellopp/README

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+
+Simple program to show gdb's "pretty print" feature on custom data types.
+In this case, two structs. One struct contains the second.
+
+Gdb's "pretty print" will use the custom printers instead of gdb's default.
+
+

tests/hellopp/hellopp.cpp

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+#include <string>
+#include <iostream>
+#include <string.h>
+
+
+struct Cell {
+    unsigned int     number;
+};
+
+struct Location {
+    std::string      city;
+    std::string      state;
+    int              zip;
+    struct Cell*     cell;
+};
+
+struct Person {
+    std::string      name;
+    int              age;
+    float            salary;
+    struct Location  location;
+};
+
+void print(const Person& person, const Location& where) {
+
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+    std::cout << "'" << person.name << "' from '" << where.city << "'." << std::endl;
+}
+
+
+int main (int argc, char** argv) {
+
+    Person me;
+    Location where;
+
+    me.name                   = "Pasveer, Ernie";
+    me.age                    = 60;
+    me.salary                 = 0.25;
+    me.location.city          = "Houston";
+    me.location.state         = "Texas";
+    me.location.zip           = 77063;
+    me.location.cell          = (Cell*)malloc(sizeof(Cell));
+    me.location.cell->number  = 2226669999;
+
+    where.city         = "Houston";
+    where.state        = "Texas";
+    where.zip          = 77063;
+    where.cell         = (Cell*)malloc(sizeof(Cell));
+    where.cell->number = 2226669999;
+
+    std::cout << "'" << me.name << "', from '" << me.location.city << "', is " << me.age << " years old and makes " << me.salary << " per year." << std::endl;
+
+    print(me, where);
+
+    free(me.location.cell);
+    free(where.cell);
+
+    me.location.cell = 0;
+    where.cell = 0;
+
+    return 0;
+}
+