stuianna / embeddedcodesizecomparison

Compares binary code size for different C++ driver and utility architectures

C++ OO Method's Code Size Comparison

Compares the resulting code size for a simple UART driver and buffer utility development using four different C++ 'object orientated' methods:

• Using pure static classes.
• Using concrete classes.
• Using polymorphic 'interface' classes
• Using static polymorphism with CRTP.

Each branch contains the incremental driver development. The goal of this codebase is solely to determine the code size overhead of implementing dependency injection to support test driven development. The run-time effect of polymorphism is not taken into account.

A general look at difference between the assembly generated by each method can be found at godbolt.

Overall Code Size

The code size of the driver and utility was calculated using the 'dec' column output of arm-none-eabi-size on the .elf of the binary for each additional function added to the program. An overall analysis of the code size is:

Incremental Code Size

One Polymorphic Function (Branch: oneFunction)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1308	8	32	1348	100.00 %
UART Driver as only concrete CPP classes	1380	8	32	1420	105.34 %
UART Driver as polymorphic CPP class	1404	8	32	1444	107.12 %
UART Driver as CRTP CPP class	1496	8	32	1536	113.94 %

Two Polymorphic Functions (Branch: twoFunctions)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1364	8	32	1404	100.00 %
UART Driver as only concrete CPP classes	1468	8	32	1508	107.40 %
UART Driver as polymorphic CPP class	1504	8	32	1544	109.97 %
UART Driver as CRTP CPP class	1616	8	32	1656	117.94 %

Three Polymorphic Functions (Branch: threeFunctions)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1440	8	32	1480	100.00 %
UART Driver as only concrete CPP classes	1592	8	32	1632	110.27 %
UART Driver as polymorphic CPP class	1732	8	32	1772	119.72 %
UART Driver as CRTP CPP class	1744	8	32	1784	120.54 %

Four Polymorphic Functions (Branch: fourFunctions)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1516	8	40	1564	100.00 %
UART Driver as only concrete CPP classes	1692	8	32	1732	110.74 %
UART Driver as polymorphic CPP class	1832	8	32	1872	119.69 %
UART Driver as CRTP CPP class	1876	8	32	1916	122.50 %

Five Polymorphic Functions (Branch: fiveFunctions)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1548	8	40	1596	100.00 %
UART Driver as only concrete CPP classes	1740	8	32	1780	111.52 %
UART Driver as polymorphic CPP class	1896	8	32	1936	121.30 %
UART Driver as CRTP CPP class	1948	8	32	1988	124.56 %

Six Polymorphic Functions (Branch: sixFunctions)

Program Type	Text	Data	BSS	Total	Relative Size
Empty CPP Program	864	8	32	904	NA
UART Driver as fully static CPP classes	1740	8	40	1788	100.00 %
UART Driver as only concrete CPP classes	1944	8	32	1984	110.96 %
UART Driver as polymorphic CPP class	2128	8	32	2168	121.25 %
UART Driver as CRTP CPP class	2192	8	32	2232	124.83 %

Running the Examples

1. Clone the repository.
2. Switch the master branch.
3. Run make analyse to build all examples, display the code size for each step and generate a graphical output.