GCC Explorer - an interactive take on compilation [LWN.net]

GCC Explorer - an interactive take on compilation

Posted Jul 3, 2012 3:32 UTC (Tue) by Richard_J_Neill (subscriber, #23093)
In reply to: GCC Explorer - an interactive take on compilation by Richard_J_Neill
Parent article: GCC Explorer - an interactive take on compilation

Much more significantly, what about an embedded system. On an Arduino, the runtime and storage costs of printf are severe. (typically ~3% of ROM)

So for example, I want to write:

#define OSC_MHZ 25
#define CLOCK_NS (1000/OSC_MHZ)
#define STRINGIGFY(s) STRINGIFY2(s)
#define STRINGIFY2(s) #s

Serial.print ("Clock period is " STRINGIFY(CLOCK_NS) "ns\n");

...which should print: "Clock period is 40 ns\n"
but actually prints: "Clock period is (1000/25 ns\n")

This sort of thing can't be done in the preprocessor and it's too expensive to do at runtime. The only workaround seems to be to actually manually: #define CLOCK_NS_STR "40"
which is a bug just waiting to happen.

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