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gcc/picolibc: Disable -fprintf-return-value when printf is not complete

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GCC will compute expected sprintf (et al) return values internally and use
them in place of the actual return value. When the printf implementation
has reduced functionality, gcc may compute a different value.

For picolibc, this means disabling the optimization unless floating point
output is enabled.

Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Keith Packard 2022-10-13 15:04:00 -07:00 • committed by Stephanos Ioannidis
commit b3073f0099
3 changed files with 9 additions and 0 deletions
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5
CMakeLists.txt
View file

@ -275,6 +275,11 @@ if(NOT CONFIG_PICOLIBC)
zephyr_compile_options($<$<COMPILE_LANGUAGE:ASM>:$<TARGET_PROPERTY:compiler,freestanding>>)
endif()
if (CONFIG_PICOLIBC AND NOT CONFIG_PICOLIBC_IO_FLOAT)
# @Intent: Set compiler specific flag to disable printf-related optimizations
zephyr_compile_options($<$<COMPILE_LANGUAGE:C>:$<TARGET_PROPERTY:compiler,no_printf_return_value>>)
endif()
# @Intent: Set compiler specific flag for tentative definitions, no-common
zephyr_compile_options($<TARGET_PROPERTY:compiler,no_common>)

2
cmake/compiler/compiler_flags_template.cmake
View file

@ -74,6 +74,8 @@ set_property(TARGET compiler-cpp PROPERTY no_exceptions)
# Flag for disabling rtti in C++
set_property(TARGET compiler-cpp PROPERTY no_rtti)
# Flag for disabling optimizations around printf return value
set_compiler_property(PROPERTY no_printf_return_value)
###################################################
# This section covers all remaining C / C++ flags #

2
cmake/compiler/gcc/compiler_flags.cmake
View file

@ -111,6 +111,8 @@ if (NOT CONFIG_NEWLIB_LIBC AND
set_compiler_property(APPEND PROPERTY nostdinc_include ${NOSTDINC})
endif()
set_compiler_property(PROPERTY no_printf_return_value -fno-printf-return-value)
set_compiler_property(TARGET compiler-cpp PROPERTY nostdincxx "-nostdinc++")
# Required C++ flags when using gcc