Library compilation problem
susnicek opened this issue · 7 comments
Dear @jfpoilpret,
I followed the documentation and tried to compile the fast-arduino-lib package using the command 'make CONF=UNO build'. However, the command yielded the following error:
avr-g++ -MT build/ARDUINO_UNO-16MHz/cores/fastarduino/soft_uart.o -MMD -MP -MF deps/ARDUINO_UNO-16MHz/cores/fastarduino/soft_uart.Td -mmcu=atmega328p -DF_CPU=16000000UL -DARDUINO_UNO -DNO_ABI -fno-exceptions -Wextra -flto -felide-constructors -Os -ffunction-sections -fdata-sections -mcall-prologues -g -Wall -I /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores -std=c++17 -c -o build/ARDUINO_UNO-16MHz/cores/fastarduino/soft_uart.o /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.cpp In file included from /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.cpp:15:0: /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.h:67:17: error: expected '{' before '::' token namespace serial::soft ^ /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.h:67:19: error: 'soft' in namespace '::' does not name a type namespace serial::soft ^ /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.h:176:39: error: expected '}' before end of line /media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/cores/fastarduino/soft_uart.h:176:39: error: expected declaration before end of line make: *** [/media/data/Documents/Elektro/FastArduino/fast-arduino-lib-master/Makefile-common.mk:131: build/ARDUINO_UNO-16MHz/cores/fastarduino/soft_uart.o] Error 1
My compilation attempt was performed under the Debian Linux 4.19.37-5 (Sid), version of my avr-g++ is 5.4.0. Any advice on this issue?
Best regards, Susnicek
Probably, my avr-g++ version is too old...
Ok, I used older syntax for nested namespaces in soft_uart.h, line 67
namespace serial { namespace soft { ...}}
...and the compilation was successful.
I thought, that the compiler's switch '-std=c++17' would do all magic, even if the 'avr-g++' version is not the latest, but it would not...
Maybe, it is better to use the old (and ugly) syntax, the most users have older compilers - even me with Debian Unstable distribution.
Best regards, Susnicek
Hi Suscnicek,
yes your avr-g++ version is pretty old. Nested namespaces (part of C++17 standard) are not supported by g++ version before 6.0.
However, even g++6.0 is not supporting all C++17 standard features and I am not sure 6.0 support would be enough for FastArduino.
In particular, there is much better support for constexpr functions in C++17 which allow simpler definitions of such functions (without such support, it is not possible to have more than one return in a constexpr function, which makes writing such functions more complex and reduces their readability).
For what it's worth, FastArduino is built (on my setup) with avr-g++ 7.4 with various C++17 features (nested namespaces and improved constexpr functions at least), and I don't have plans to support older versions as this is the recipe for bad-looking source code; note that even g++7.4 is not that new actually (released in 2017 I think), but this was the latest version available for AVR targets on fedora distrib, which is my distrib of choice on all my workstations). I generally reserve Debian for servers only (plus Raspberry Pi with raspbian distro).
Dear @jfpoilpret ,
thank you for your answer. It is ok for me now, I can use the libraries with the slight modification (or maybe later I will try to compile the avr-gcc sources etc.).
One think is not clear to me: the compiler complained on the nested namespace in 'soft_uart.h' but it did not complain on the same thing in 'uart.h'. I only needed to modify the file 'uart_soft.h' to compile the library. Strange...
Susnicek
Hi @susnicek
I think the main reason why the compiler did not complain for uart.h is that it did not compile anything including uart.h (headers are not compiled during library building only .cpp source files).
soft_uart.h gets parsed by the compiler because it is included in soft_uart.cpp which must be compiled.
When you will use (in an application) FastArduino headers, you may get more of this error. In particular, if you use FastArduino headers for devices support, nested namespaces are also used there.
So in the end, you will need to change nested namespaces whenever you include headers where they exist.
Issue has been answered and can be closed.
Yes, you were right.
Thank you!