Board: Teensy 3.6
Toolchain-version: teensy-compile/15.2.1
Sketch to reproduce:
When using an unordered_map, the Linker does not find a floor() reference:
I don't have much experience with the inner workings of the c++ compiler/linker toolchain so I had Claude walk me through it and it ended up suggesting me this working way to resolve this:
in "~/.arduino15/packages/teensy/hardware/avr/1.62.0/boards.txt"
find "teensy36.build.flags.libs=-larm_cortexM4lf_math -lm -lstdc++"
change it to "teensy36.build.flags.libs=-larm_cortexM4lf_math -Wl,--start-group -lm -lstdc++ -Wl,--end-group"
So that ld rescans them until everything resolves as (if I get it right) unordered_maps dependancy of floor() is realized at the -lstdc step but floor() would be found at the -lm step, but as the -lm step is already done, the linker does not revisit it to resolve the floor() dependancy.
With the two arguments grouped, the linker can revisit them which resolves this.
I don't know if this way to resolve this imposes other things not wanted by Teensyduino, I just wanted to resolve this issue for me and help the ones looking for this after me.
I hope that this gets fixed in the next toolchain-version as it would overwrite this change made in the boards.txt.
Feel free point me to relevant other issues if this is a duplicate of anything
Toolchain-version: teensy-compile/15.2.1
Sketch to reproduce:
C++:
using namespace std;
unordered_map<int, int> floormap_stepper = {{1, 1}};
void setup() {}
void loop() {}When using an unordered_map, the Linker does not find a floor() reference:
Code:
Linking everything together...
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/arm-none-eabi-gcc -O2 -Wl,--gc-sections,--relax,--no-warn-rwx-segments,--defsym=__rtc_localtime=1784903286 -T/home/benji/.arduino15/packages/teensy/hardware/avr/1.62.0/cores/teensy3/mk66fx1m0.ld -mthumb -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16 -fsingle-precision-constant -o /home/benji/.cache/arduino/sketches/9F9B2C8D6A15A62AB1000E144EF731B7/sketch_jul24a.ino.elf /home/benji/.cache/arduino/sketches/9F9B2C8D6A15A62AB1000E144EF731B7/sketch/sketch_jul24a.ino.cpp.o /home/benji/.cache/arduino/sketches/9F9B2C8D6A15A62AB1000E144EF731B7/core/core.a -L/home/benji/.cache/arduino/sketches/9F9B2C8D6A15A62AB1000E144EF731B7 -larm_cortexM4lf_math -lm -lstdc++
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o): in function `std::__detail::_Prime_rehash_policy::_M_next_bkt(unsigned int) const':
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy11_M_next_bktEj+0x68): undefined reference to `floor'
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: (floor): Unknown destination type (ARM/Thumb) in /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o)
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy11_M_next_bktEj+0x68): dangerous relocation: unsupported relocation
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy11_M_next_bktEj+0xa2): undefined reference to `floor'
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: (floor): Unknown destination type (ARM/Thumb) in /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o)
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy11_M_next_bktEj+0xa2): dangerous relocation: unsupported relocation
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o): in function `std::__detail::_Prime_rehash_policy::_M_need_rehash(unsigned int, unsigned int, unsigned int) const':
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy14_M_need_rehashEjjj+0x60): undefined reference to `floor'
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: (floor): Unknown destination type (ARM/Thumb) in /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o)
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy14_M_need_rehashEjjj+0x60): dangerous relocation: unsupported relocation
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy14_M_need_rehashEjjj+0x96): undefined reference to `floor'
/home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/bin/ld: (floor): Unknown destination type (ARM/Thumb) in /home/benji/.arduino15/packages/teensy/tools/teensy-compile/15.2.1/arm/bin/../lib/gcc/arm-none-eabi/15.2.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libstdc++.a(hashtable_c++0x.o)
hashtable_c++0x.cc:(.text._ZNKSt8__detail20_Prime_rehash_policy14_M_need_rehashEjjj+0x96): dangerous relocation: unsupported relocation
collect2: error: ld returned 1 exit status
exit status 1I don't have much experience with the inner workings of the c++ compiler/linker toolchain so I had Claude walk me through it and it ended up suggesting me this working way to resolve this:
in "~/.arduino15/packages/teensy/hardware/avr/1.62.0/boards.txt"
find "teensy36.build.flags.libs=-larm_cortexM4lf_math -lm -lstdc++"
change it to "teensy36.build.flags.libs=-larm_cortexM4lf_math -Wl,--start-group -lm -lstdc++ -Wl,--end-group"
So that ld rescans them until everything resolves as (if I get it right) unordered_maps dependancy of floor() is realized at the -lstdc step but floor() would be found at the -lm step, but as the -lm step is already done, the linker does not revisit it to resolve the floor() dependancy.
With the two arguments grouped, the linker can revisit them which resolves this.
I don't know if this way to resolve this imposes other things not wanted by Teensyduino, I just wanted to resolve this issue for me and help the ones looking for this after me.
I hope that this gets fixed in the next toolchain-version as it would overwrite this change made in the boards.txt.
Feel free point me to relevant other issues if this is a duplicate of anything
