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2 Commits

Author SHA1 Message Date
J. Nick Koston
2b70e62df5 tweak 2026-02-01 12:48:21 +01:00
J. Nick Koston
dcab2def05 no scanf float 2026-02-01 12:47:14 +01:00
2 changed files with 52 additions and 0 deletions

View File

@@ -205,6 +205,7 @@ async def to_code(config):
"pre:testing_mode.py",
"pre:exclude_updater.py",
"pre:exclude_waveform.py",
"pre:remove_float_scanf.py",
"post:post_build.py",
],
)
@@ -342,3 +343,8 @@ def copy_files() -> None:
exclude_waveform_file,
CORE.relative_build_path("exclude_waveform.py"),
)
remove_float_scanf_file = dir / "remove_float_scanf.py.script"
copy_file_if_changed(
remove_float_scanf_file,
CORE.relative_build_path("remove_float_scanf.py"),
)

View File

@@ -0,0 +1,46 @@
# pylint: disable=E0602
Import("env") # noqa
# Remove forced scanf linkage to allow garbage collection of unused code
#
# The ESP8266 Arduino framework unconditionally adds:
# -u _printf_float -u _scanf_float
#
# The -u flag forces symbols to be linked even if unreferenced, which pulls
# in the entire scanf family (~7-8KB). ESPHome doesn't use scanf at all
# (verified by CI check in PR #13657), so this is pure dead weight.
#
# By removing -u _scanf_float, --gc-sections can eliminate:
# - scanf family functions (~7KB)
# - _strtod_l (~3.7KB)
# - Related parsing infrastructure
#
# We keep -u _printf_float because components still use %f in logging.
def remove_scanf_float_flag(source, target, env):
"""Remove -u _scanf_float from linker flags.
This is called as a pre-action before the link step, after the
Arduino framework has added its default flags.
"""
linkflags = env.get("LINKFLAGS", [])
new_linkflags = []
i = 0
while i < len(linkflags):
flag = linkflags[i]
if flag == "-u" and i + 1 < len(linkflags):
next_flag = linkflags[i + 1]
if next_flag == "_scanf_float":
print("ESPHome: Removing _scanf_float (saves ~8KB flash)")
i += 2 # Skip both -u and the symbol
continue
new_linkflags.append(flag)
i += 1
env.Replace(LINKFLAGS=new_linkflags)
# Register the callback to run before the link step
env.AddPreAction("$BUILD_DIR/${PROGNAME}.elf", remove_scanf_float_flag)