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Speed up empty String creation slightly (#6573)

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As @dirkmuller found out in #6568, there is a difference in code
executed between `String str(nullptr)` and `String str("")`, but in the
end the actual object is identical.  It's a few bytes of code, but every
little bit counts.

Update the default `String()` constructor to use `nullptr` and not `""`.
This will remove a constant literal load and the execution of the
String::copy method and strlen().
This commit is contained in:
Earle F. Philhower, III 2019-09-30 22:35:23 -07:00 committed by Develo
parent 1d26b28225
commit 1aeea124b3
1 changed files with 1 additions and 1 deletions
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cores/esp8266/WString.h
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@ -53,7 +53,7 @@ class String {
// if the initial value is null or invalid, or if memory allocation
// fails, the string will be marked as invalid (i.e. "if (s)" will
// be false).
String(const char *cstr = "");
String(const char *cstr = nullptr);
String(const String &str);
String(const __FlashStringHelper *str);
#ifdef __GXX_EXPERIMENTAL_CXX0X__