GCC - Compiling and Linking
This section tells you what options to use from the millions that GCC provides (sometimes choice is a daunting prospect):
Health Warning: Mostly under Construction
Compiler options
We use 4 compiler strings
Optimized by Size
Optimized by Time
Not Optimization
Debugging
In the case of problems or unexpected results we use an assembler output to see what the compiler is doing. Typically this uses an unoptimized compilation but sometimes you need to see EXACTLY what the compiler is doing. These compiler guys are supper smart and 'hoist' code all over the place to get the best results - an optimzed assembler listing can be very confusing - but that's why you are a programmer 'cos you like confusing stuff!
Notes:
- We use C only in development and have no particular axe to grind so we use the current (3.0.4) language default of 'gnu89' (ISO C89 standard plus some gnu extensions). If your stuff won't compile you may have to play around with the -x options.
The -traditional flag means Kerrigan & Richie so if your code was built after reading their great book you may have to use his option.
| Option |
Function |
| -g |
Include debugging information for GDB - it does no harm to include this always. |
| -mcpu=860 |
This includes the 850, 855T and all their variants. |
| -S |
Stop when an assembly listing has been created - but do not run the assembler. |
| -fverbose-asm |
Create an annotated assembly listing. |
| -c |
Stop when there is an object file (do C -> assembler, then run assembler) but do not link. |
| -o |
(Little letter O) defines the destination file. |
| -fno-hosted |
Assume no library functions. |
| -Os |
Optimize for speed. |
| -O3 |
Maximum optimisation almost no chance of de-bugging sensibly. |
| -O |
Mimimum optimisation - you stand a chance of de-bugging sensibly. |
| -O0 |
(Letter 0 with number 0)No optimisation. |
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