Commit 27438f60 authored by hjk's avatar hjk Committed by hjk

add some example with statistics on the impact of using small classes

Change-Id: I29c68ce88fef599091a84f8bdec54778e4d62b03
Reviewed-on: http://codereview.qt-project.org/5257Reviewed-by: default avatarhjk <qthjk@ovi.com>
parent 0cea87f5
Running test.sh tests several replacement patterns for a typical case
of polymorphism, and creates some statistics of the output.
The 'critical' case is where the implementation is only instantiated
from a single location.
'Symbols' refers to the number of additional symbols created by the
pattern (relevant for relocation on application startup and debugger
performance)
'Size' refers to the size of the '.text' section, i.e. the 'generated
code'.
'Debug' is the size of the .debug_info section in the binary.
Note that the numbers are not directly comparable. As the 'Slim'
versions push code from the implementation to the user side, the
ratio will be "better" when the the implementation is instantiated
from more than one place.
Interface/Implementation (out of line)
Symbols: 13
Size: 2388
Debug: 4541
Interface/Implementation (non-virtual)
Symbols: 13
Size: 2388
Debug: 4431
Interface/Implementation (inline)
Symbols: 12
Size: 2643
Debug: 4402
Merged
Symbols: 7
Size: 2447
Debug: 4342
Slimmest possible
Symbols: 0
Size: 1971
Debug: 4246
#!/bin/bash
export CXX="g++ -O3 -g "
function stat() {
echo -e ""
echo -e "Symbols: $(nm $@ | grep ' [TVW] ' | grep _Z | grep -v "_ZNSs" | wc -l)"
echo -e "Size: $(size -d -B $@ | tail -1 | cut -c1-10)"
echo -e "Debug: $(echo "ibase=16;"$(readelf -S $@ | grep debug_info | cut -c50-56 | tr a-f A-F) | bc)"
echo -e ""
echo -e ""
# echo -e "Symbols: $(nm "$@" | grep ' [TUVW] '| grep _Z )"
}
function test_1() {
echo "Interface/Implementation (out of line)"
cat > interface_1.h <<EOF
#include <string>
struct Interface { virtual ~Interface() {} virtual std::string func() const = 0; };
EOF
cat > implementation_1.h <<EOF
#include "interface_1.h"
struct Implementation : Interface { std::string func() const; };
EOF
cat > implementation_1.cpp <<EOF
#include "implementation_1.h"
std::string Implementation::func() const { return "Test1"; }
EOF
cat > main_1.cpp <<EOF
#include "implementation_1.h"
int main() { Interface *x = new Implementation(); return x->func().size(); }
EOF
$CXX implementation_1.cpp main_1.cpp -o test_1
stat test_1
}
function test_2() {
echo "Interface/Implementation (non-virtual)"
cat > interface_2.h <<EOF
#include <string>
struct Interface { virtual ~Interface() {} virtual std::string func() const = 0; };
EOF
cat > implementation_2.h <<EOF
#include "interface_2.h"
struct Implementation : Interface {
~Implementation() {} std::string func() const { return "Test2"; } };
EOF
cat > main_2.cpp <<EOF
#include "implementation_2.h"
int main() { Interface *x = new Implementation(); return x->func().size(); }
EOF
$CXX main_2.cpp -o test_2
stat test_2
}
function test_3() {
echo "Interface/Implementation (inline)"
cat > interface_3.h <<EOF
#include <string>
struct Interface
{
virtual ~Interface() {}
std::string func() const { return m_data; }
std::string m_data;
};
EOF
cat > implementation_3.h <<EOF
#include "interface_3.h"
struct Implementation : Interface {
Implementation() { m_data = "Test3"; }
};
EOF
cat > main_3.cpp <<EOF
#include "implementation_3.h"
int main() { Interface *x = new Implementation(); return x->func().size(); }
EOF
$CXX main_3.cpp -o test_3
stat test_3
}
function test_4() {
echo "Merged"
cat > interface_4.h <<EOF
#include <string>
struct Interface
{
virtual ~Interface() {}
std::string func() const { return m_data; }
void setData(const std::string &data) { m_data = data; }
private:
std::string m_data;
};
EOF
cat > implementation_4.h <<EOF
#include "interface_4.h"
void setupImplementation(Interface *i) { i->setData("Test4"); }
EOF
cat > main_4.cpp <<EOF
#include "implementation_4.h"
int main() { Interface *x = new Interface(); setupImplementation(x); return x->func().size(); }
EOF
$CXX main_4.cpp -o test_4
stat test_4
}
function test_5() {
echo "Slimmest possible"
cat > interface_5.h <<EOF
#include <string>
struct Interface
{
std::string func() const { return m_data; }
void setData(const std::string &data) { m_data = data; }
private:
std::string m_data;
};
EOF
cat > main_5.cpp <<EOF
#include "interface_5.h"
int main() { Interface *x = new Interface(); x->setData("Test4"); return x->func().size(); }
EOF
$CXX main_5.cpp -o test_5
stat test_5
}
function test_6() {
echo "Constructor"
cat > interface_6.h <<EOF
#include <string>
struct Interface
{
explicit Interface(const std::string &data) : m_data(data) {}
std::string func() const { return m_data; }
private:
const std::string m_data;
};
EOF
cat > main_6.cpp <<EOF
#include "interface_6.h"
int main() { Interface *x = new Interface("Test4"); return x->func().size(); }
EOF
$CXX main_6.cpp -o test_6
stat test_6
}
function main() {
test_1
test_2
test_3
test_4
test_5
#test_6
}
main
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