std::string vs char array for static const

Question

I want to use a string constant in multiple places in my cpp file. Should I use std::string or char[]?

static const std::string kConstantString = "ConstantStringValue";

static const char kConstantString[] = "ConstantStringValue";

I was told to prefer the latter since it "avoids static allocation". Doesn't the char array also have to be statically allocated?

The main reason I would prefer static const char[] is to avoid the object fingerprint of std::string. Are you dealing with such strict limitations? — Dimitrios Bouzas
– Dimitrios Bouzas, Commented Jun 11, 2015 at 22:25
This may help you understand.....Personally, I would use std::string..... — ha9u63a7
– ha9u63a7, Commented Jun 11, 2015 at 22:25
@101010: The, ehm, what? "Object fingerprint"? What's that, then? — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Jun 11, 2015 at 22:35
@LightnessRacesinOrbit I mean size with std::string you carry an extra size attributed to the class. — Dimitrios Bouzas
– Dimitrios Bouzas, Commented Jun 11, 2015 at 22:40
In this demo you can see that with std::string you carry an extra burden of 32 bytes which is attributed to the class.` — Dimitrios Bouzas
– Dimitrios Bouzas, Commented Jun 11, 2015 at 22:55

Puppy · Accepted Answer · 2015-06-11 22:29:16Z

4

Yes, yes it does also have to be statically allocated.

Always use std::string unless your profiler tells you that it's worth pissing around with legacy crap like const char[]. Choosing const char[] is an annoying micro-optimization over std::string and a stupid decision unless you know for sure that this piece of code is a hotpath (since it's static either way I highly doubt it).

answered Jun 11, 2015 at 22:29

Puppy

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2 Comments

Synxis Over a year ago

Downvoted. Using static const std::string is a recipe for disaster because of the static initialization order fiasco, someone might inadvertely use it in other static constants. I actually saw it happens several times...

micha Over a year ago

-1: No, no allocations are happening. Static const char* strings will get a special location in the binary (RO section). Nothing got malloc'd, it's simply "there" to be accessed. Static std::string does require static initialization and thus you're opening yourself up for SIOF, like @Synxis mentioned.

Vlad from Moscow · Accepted Answer · 2015-06-11 22:40:03Z

4

Simply define a pointer to this string literal.:) It can have static storage specifier.

There is no any need to use class std::string. It is simply redundant and uselessly. This constant always can be converted to std::string if it is indeed required.

edited Jun 11, 2015 at 22:40

answered Jun 11, 2015 at 22:32

Vlad from Moscow

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1 Comment

Lightness Races in Orbit Over a year ago

Aside from all the reasons you forgot/ignored, sure.

Lightness Races in Orbit · Accepted Answer · 2015-06-11 23:07:53Z

0

Since it's a static const, you won't be able to do any manipulation on this string anyway, so it is better to just use const char[].

edited Jun 11, 2015 at 23:07

Lightness Races in Orbit

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answered Jun 11, 2015 at 22:38

maayanwis

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1 Comment

underscore_d Over a year ago

What about read-only 'manipulation'? Things like getting the length or concatenating it into another string would be a lot easier if one could use the std::string functions rather than trudging through strcat() et al. Sure, if it's just a label and won't be entered into any manipulation, then maybe the char is fine - but let's not oversimplify (like all the other answers here...)

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