After updating the Arduino ESP8266 core from 2.4.7 to 3.0.0 or upwards I seem to be getting a set of compilation errors, different to the ones reported by other users a while ago. This I initially found when using an earlier version of B4R but also the same for B4R 3.90. A small section of the error log is shown below but the rest is of similar gist:
Comp Err:
In file included from C:\B4R\tt1\Objects\bin\sketch\B4RDefines.h:24,
from C:\B4R\tt1\Objects\bin\sketch\b4r_main.cpp:1:
C:\B4R\tt1\Objects\bin\sketch\b4r_main.cpp: In static member function 'static void b4r_main::_afterreset()':
rCore.h:497:61: error: call of overloaded 'abs(ULong)' is ambiguous
497 | #define /*Double Abs(Double Number);*/ Common_Abs(n) abs(n)
| ^
C:\B4R\tt1\Objects\bin\sketch\b4r_main.cpp:455:18: note: in expansion of macro 'Common_Abs'
455 | _dift = (ULong) (Common_Abs(b4r_main::_starttime-Common_Millis()));
| ^~~~~~~~~~
In file included from c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\c++\10.3.0\cstdlib:75,
from c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\c++\10.3.0\stdlib.h:36,
from C:\Users\BRT\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.0.2\cores\esp8266/Arduino.h:27,
from C:\B4R\tt1\Objects\bin\sketch\B4RDefines.h:8,
from C:\B4R\tt1\Objects\bin\sketch\b4r_main.cpp:1:
c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\stdlib.h:74:5: note: candidate: 'int abs(int)'
74 | int abs (int);
| ^~~
In file included from c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\c++\10.3.0\cstdlib:77,
from c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\c++\10.3.0\stdlib.h:36,
from C:\Users\BRT\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.0.2\cores\esp8266/Arduino.h:27,
from C:\B4R\tt1\Objects\bin\sketch\B4RDefines.h:8,
from C:\B4R\tt1\Objects\bin\sketch\b4r_main.cpp:1:
c:\users\brt\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\xtensa-lx106-elf\include\c++\10.3.0\bits\std_abs.h:79:3: note: candidate: 'constexpr long double std::abs(long double)'
79 | abs(long double __x)
| ^~~