cstdio name collision solution

[diggit]

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I had issues with name collision when including cstdio #66. Solution with mapping to wrap functions is taken from bisqwit/tinyprintf. What do you think about it?

Consider this a quick POC rather than a final code solution.

[codecov-io]

Codecov Report

Merging #74 (92e71f3) into master (d3b9846) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #74   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          359       359           
=========================================
  Hits           359       359           

Impacted Files	Coverage Δ
printf.c	100.00% <100.00%> (ø)

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Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update d3b9846...66e17f1. Read the comment docs.

[mpaland]

Hi Patrik, what exactly is the problem with the trailing underscore? Is it defined that way in your cstudio?

[diggit]

trailing underscore is not a problem, macros like #define printf printf_ are. When I comment them out, error is gone.

Error:

[1/3] Building CXX object CMakeFiles/TLM.elf.dir/src/main.cpp.obj
FAILED: CMakeFiles/TLM.elf.dir/src/main.cpp.obj 
/usr/bin/arm-none-eabi-g++   -I../src -I../src/printf -I../src/span/include/tcb -I../src/CMSIS/CMSIS/Core/Include -I../src/CMSIS/CMSIS/DSP/Include -I../src/CMSIS/CMSIS/DSP/Source -fno-builtin -Wall -ffunction-sections -fdata-sections -fomit-frame-pointer -mabi=aapcs -std=c++11  -D 'BUILD=385' -D 'GIT_VERSION_SHORT=3256378' -Dtimegm=mktime -DDEBUG=1 -DSTM32F446=1 -DHWVERSION=12 -DTCB_SPAN_NO_EXCEPTIONS -DMPRINTF_DISABLE_DIRECT_MAPPING -Werror=switch -Werror=return-type -Werror=stringop-overflow -Werror=parentheses -Wfatal-errors -Wno-unused-function  -Wall -Wextra -Wundef -Wduplicated-cond -Wduplicated-branches -Wlogical-op -Wnull-dereference -Wcast-align -Wvla -Wmissing-format-attribute -Wuninitialized -Winit-self -Wdouble-promotion -Wstrict-aliasing -Wno-unused-local-typedefs -funwind-tables -Wno-unused-parameter -pedantic -g -Og  -mthumb -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -funsigned-char -funsigned-bitfields -ffunction-sections -fdata-sections -fdiagnostics-color=always -fstack-protector-strong -finline-small-functions -findirect-inlining -Wint-to-pointer-cast -Weffc++ -std=c++2a -Wno-register -fno-rtti -fno-exceptions -fno-threadsafe-statics -MD -MT CMakeFiles/TLM.elf.dir/src/main.cpp.obj -MF CMakeFiles/TLM.elf.dir/src/main.cpp.obj.d -o CMakeFiles/TLM.elf.dir/src/main.cpp.obj -c ../src/main.cpp
In file included from ../src/main.cpp:19:
/usr/arm-none-eabi/include/c++/9.2.0/cstdio:137:11: error: '::sprintf' has not been declared
  137 |   using ::sprintf;
      |           ^~~~~~~
compilation terminated due to -Wfatal-errors.
[2/3] Building C object CMakeFiles/TLM.elf.dir/src/printf/printf.c.obj
ninja: build stopped: subcommand failed.

/*line 18*/ #include "printf/printf.h"
/*line 19*/ #include <cstdio>

If I swap them, error is different:

[1/2] Building CXX object CMakeFiles/TLM.elf.dir/src/main.cpp.obj
FAILED: CMakeFiles/TLM.elf.dir/src/main.cpp.obj 
/usr/bin/arm-none-eabi-g++   -I../src -I../src/printf -I../src/span/include/tcb -I../src/CMSIS/CMSIS/Core/Include -I../src/CMSIS/CMSIS/DSP/Include -I../src/CMSIS/CMSIS/DSP/Source -fno-builtin -Wall -ffunction-sections -fdata-sections -fomit-frame-pointer -mabi=aapcs -std=c++11  -D 'BUILD=385' -D 'GIT_VERSION_SHORT=3256378' -Dtimegm=mktime -DDEBUG=1 -DSTM32F446=1 -DHWVERSION=12 -DTCB_SPAN_NO_EXCEPTIONS -DMPRINTF_DISABLE_DIRECT_MAPPING -Werror=switch -Werror=return-type -Werror=stringop-overflow -Werror=parentheses -Wfatal-errors -Wno-unused-function  -Wall -Wextra -Wundef -Wduplicated-cond -Wduplicated-branches -Wlogical-op -Wnull-dereference -Wcast-align -Wvla -Wmissing-format-attribute -Wuninitialized -Winit-self -Wdouble-promotion -Wstrict-aliasing -Wno-unused-local-typedefs -funwind-tables -Wno-unused-parameter -pedantic -g -Og  -mthumb -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -funsigned-char -funsigned-bitfields -ffunction-sections -fdata-sections -fdiagnostics-color=always -fstack-protector-strong -finline-small-functions -findirect-inlining -Wint-to-pointer-cast -Weffc++ -std=c++2a -Wno-register -fno-rtti -fno-exceptions -fno-threadsafe-statics -MD -MT CMakeFiles/TLM.elf.dir/src/main.cpp.obj -MF CMakeFiles/TLM.elf.dir/src/main.cpp.obj.d -o CMakeFiles/TLM.elf.dir/src/main.cpp.obj -c ../src/main.cpp
In file included from ../src/main.cpp:19:
/usr/arm-none-eabi/include/c++/9.2.0/bits/basic_string.h: In function 'std::string std::__cxx11::to_string(int)':
../src/printf/printf.h:86:19: error: 'vsnprintf_' is not a member of 'std'; did you mean 'isprint'?
   86 | #define vsnprintf vsnprintf_
      |                   ^~~~~~~~~~
compilation terminated due to -Wfatal-errors.
ninja: build stopped: subcommand failed.

[diggit]

With this wrap workaround, you have to include normal printf headers (<cstdio>) and calls to printf get remapped to __wrap_printf at link time.

[mpaland]

Uiii, I see, the macro defines create problems. Unusual, but existent. Going to merge your PS soon.

[diggit]

I am open to suggestion for improvements, like styling etc.

Also some note about this problem and how to solve it should be put somewhere. Readme or comment in code?

When someone want to use wrapping method in c++, should we suggest to directly include <cstdio> or rather embed inclusion into printf.h via some macro (preferred because in C, you would have to include stdio.h and including one header might be easier)?

[diggit]

A have new way of name collision avoidance. Function names are prefixed by default by mp_ prefix (your nickname shortened). To alter function names, simple macro can be added via compiler flags. Eg -D'PRINTF_FUNCTION_RENAME\(base\)=__wrap_\#\#base' gives all functions __wrap_ prefix (eg. __wrap_printf) to allow link time substitution. Adding -D'PRINTF_FUNCTION_RENAME\(base\)=base' gives functions their native names etc... Tested with cmake. Character escaping may differ in other build systems. This implementation alters functions names and not just some mapping. Thus making possible that __wrap_ magic.