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

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>
Willmish · Oct 31, 2022 · b3073f0 · b3073f0
1 parent cb5c440
commit b3073f0
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diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -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>)
 

diff --git a/cmake/compiler/compiler_flags_template.cmake b/cmake/compiler/compiler_flags_template.cmake
@@ -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 #

diff --git a/cmake/compiler/gcc/compiler_flags.cmake b/cmake/compiler/gcc/compiler_flags.cmake
@@ -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