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