valgrind: WString: strings overlap

[d-a-v]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: any
• Core Version: git
• Development Env: other: host emulation
• Operating System: linux

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Problem Description

valgrind complains with core/esp8266/WString.cpp:

Source and destination overlap in strcpy(0x1fff0000e0, 0x1fff0000e0)

MCVE Sketch

void setup ()
{
        String blah = "blah";
        blah.replace("xx","y");
}

void loop ()
{
}

How to reproduce:

cd tests/host
mkdir -p ino/WString
# put MCVE in ino/WString/WString.ino
make -j FORCE32=0 ino/WString/WString
# ...
valgrind bin/WString/WString

line 747:

Arduino/cores/esp8266/WString.cpp

Line 747 in f0eb550

strcpy(writeTo, readFrom);

[TD-er]

It looks like the fix needs to: (first two are too obvious, but just for completeness)

• check pointers differ
• determine nr of bytes to move/copy
• Do not use copy, but use memmove (see warnings at both memcpy and strcpy)

N.B. memcpy is used at more places in the same function on the same arrays.