commit #7611 breaks compiler optimisation

[5chufti]

Basic Infos

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

Platform

• Hardware: []
• Core Version: [latest git]
• Development Env: [Arduino IDE]
• Operating System: [Windows]

Settings in IDE

• Module: [Generic ESP8266 Module]
• Flash Mode: [dout]
• Flash Size: [1MB]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [nodemcu]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [115200] (serial upload only)

Problem Description

referenced commmit breaks use of any optimisation above -Os
at link time there are curious missing symbols ...

MCVE Sketch

void setup() {
  Serial.begin(74880); 
  pinMode(LED_BUILTIN, OUTPUT);
  while (!Serial) ; // wait for Arduino Serial Monitor
}

void loop() {
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
    delay(500);
}

Debug Messages

Linking everything together...
"D:\\arduino\\portable\\packages\\esp8266\\tools\\xtensa-lx106-elf-gcc\\3.0.0-gnu12/bin/xtensa-lx106-elf-gcc" -CC -E -P -DVTABLES_IN_FLASH "D:\\arduino\\portable\\packages\\esp8266\\hardware\\esp8266\\3.0.0/tools/sdk/ld/eagle.app.v6.common.ld.h" -o "C:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451/local.eagle.app.v6.common.ld"
"D:\\arduino\\portable\\packages\\esp8266\\tools\\xtensa-lx106-elf-gcc\\3.0.0-gnu12/bin/xtensa-lx106-elf-gcc" -fno-exceptions -Wl,-Map "-Wl,C:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451/sketch_nov09a.ino.map" -O3 -g -Wall -Wextra -nostdlib -Wl,--no-check-sections -u app_entry -u _printf_float -u _scanf_float -Wl,-static "-LD:\\arduino\\portable\\packages\\esp8266\\hardware\\esp8266\\3.0.0/tools/sdk/lib" "-LD:\\arduino\\portable\\packages\\esp8266\\hardware\\esp8266\\3.0.0/tools/sdk/lib/NONOSDK22x_191122" "-LD:\\arduino\\portable\\packages\\esp8266\\hardware\\esp8266\\3.0.0/tools/sdk/ld" "-LD:\\arduino\\portable\\packages\\esp8266\\hardware\\esp8266\\3.0.0/tools/sdk/libc/xtensa-lx106-elf/lib" -Teagle.flash.1m.ld -Wl,--gc-sections -Wl,-wrap,system_restart_local -Wl,-wrap,spi_flash_read -o "C:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451/sketch_nov09a.ino.elf" -Wl,--start-group "C:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451\\sketch\\sketch_nov09a.ino.cpp.o" "C:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451\\core\\core.a" -lhal -lphy -lpp -lnet80211 -llwip2-536 -lwpa -lcrypto -lmain -lwps -lbearssl -lespnow -lsmartconfig -lairkiss -lwpa2 -lstdc++ -lm -lc -lgcc -Wl,--end-group "-LC:\\Users\\me\\AppData\\Local\\Temp\\arduino_build_74451"
d:/arduino/portable/packages/esp8266/tools/xtensa-lx106-elf-gcc/3.0.0-gnu12/bin/../lib/gcc/xtensa-lx106-elf/10.1.0/../../../../xtensa-lx106-elf/bin/ld.exe: C:\Users\me\AppData\Local\Temp\arduino_build_74451\core\core.a(Stream.cpp.o):(.text._ZN6Stream10readStringEv+0x4): undefined reference to `_ZN6String4initEv'
d:/arduino/portable/packages/esp8266/tools/xtensa-lx106-elf-gcc/3.0.0-gnu12/bin/../lib/gcc/xtensa-lx106-elf/10.1.0/../../../../xtensa-lx106-elf/bin/ld.exe: C:\Users\me\AppData\Local\Temp\arduino_build_74451\core\core.a(Stream.cpp.o):(.text._ZN6Stream10readStringEv+0x1b): undefined reference to `_ZN6String4initEv'
collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board Generic ESP8266 Module.

[mcspr]

Does it build after removing inline keyword here?

Arduino/cores/esp8266/WString.cpp

Line 129 in 5d2563e

inline void String::init(void) {

addendum: #7553 should actually fix this, but it is in a review limbo atm :(
Right now GCC just removes the String::init() symbol from the WString.cpp.o, since it is marked as inline

[5chufti]

yes, removing the "inline" seems to fix the issue.

[earlephilhower]

@5chufti can you please verify if #7553 (already merged) w/o any changes fixes your issue and report back?

[5chufti]

Hi, issue seems resolved with current git version.
So closing issue ...