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Use if-else chains instead of switch for string lookups
Switch statements generate CSWTCH jump tables in RAM on ESP8266. PROGMEM_STRING_TABLE causes LoadStoreError from flash cache conflicts in API subscribe paths. If-else with LOG_STR avoids both: strings stay in flash via PSTR, and comparison branches don't need a data table. Zero RAM overhead confirmed via nm.
This commit is contained in:
J. Nick Koston
@@ -6,7 +6,6 @@
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#include "crash_handler.h"
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#include "esphome/core/helpers.h"
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#include "esphome/core/log.h"
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#include "esphome/core/progmem.h"
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#include <cinttypes>
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@@ -101,71 +100,67 @@ void crash_handler_read_and_clear() {
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// Xtensa exception cause names (shared with ESP32, same ISA).
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// Keep in sync with Xtensa ISA reference manual Table 4-64.
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// Split into two PROGMEM_STRING_TABLEs to stay under 255-byte blob limit.
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// clang-format off
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PROGMEM_STRING_TABLE(ExcCauseLow, // Causes 0-9
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"IllegalInstruction", // 0
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"Syscall", // 1
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"InstructionFetchError", // 2
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"LoadStoreError", // 3
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"Level1Interrupt", // 4
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"Alloca", // 5
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"IntegerDivideByZero", // 6
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"PCValue", // 7
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"Privileged", // 8
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"LoadStoreAlignment" // 9
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);
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PROGMEM_STRING_TABLE(ExcCauseHigh, // Causes 12-29 (offset by 12)
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"InstrPDAddrError", // 12
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"LoadStorePIFDataError", // 13
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"InstrPIFAddrError", // 14
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"LoadStorePIFAddrError", // 15
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"InstTLBMiss", // 16
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"InstTLBMultiHit", // 17
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"InstFetchPrivilege", // 18
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"", // 19 (unused)
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"InstrFetchProhibited", // 20
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"", // 21 (unused)
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"", // 22 (unused)
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"", // 23 (unused)
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"LoadStoreTLBMiss", // 24
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"LoadStoreTLBMultihit", // 25
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"LoadStorePrivilege", // 26
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"", // 27 (unused)
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"LoadProhibited", // 28
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"StoreProhibited" // 29
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);
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// clang-format on
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static constexpr uint32_t EXC_CAUSE_HIGH_BASE = 12; // First cause code in ExcCauseHigh table
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// Uses if-else instead of switch to avoid CSWTCH jump tables (RAM on ESP8266).
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// PROGMEM_STRING_TABLE also crashes due to flash cache conflicts in API paths.
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// LOG_STR strings are in flash via PSTR; if-else generates comparison branches only.
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static const LogString *get_exception_cause(uint32_t cause) {
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if (cause < ExcCauseLow::COUNT)
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return ExcCauseLow::get_log_str(cause, ExcCauseLow::LAST_INDEX);
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if (cause >= EXC_CAUSE_HIGH_BASE && cause < EXC_CAUSE_HIGH_BASE + ExcCauseHigh::COUNT) {
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const LogString *str = ExcCauseHigh::get_log_str(cause - EXC_CAUSE_HIGH_BASE, ExcCauseHigh::LAST_INDEX);
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// Empty strings are gap entries — return nullptr so caller knows cause is unknown
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if (LOG_STR_ARG(str)[0] == '\0')
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return nullptr;
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return str;
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}
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if (cause == 0)
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return LOG_STR("IllegalInstruction");
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if (cause == 1)
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return LOG_STR("Syscall");
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if (cause == 2)
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return LOG_STR("InstructionFetchError");
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if (cause == 3)
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return LOG_STR("LoadStoreError");
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if (cause == 4)
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return LOG_STR("Level1Interrupt");
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if (cause == 5)
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return LOG_STR("Alloca");
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if (cause == 6)
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return LOG_STR("IntegerDivideByZero");
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if (cause == 7)
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return LOG_STR("PCValue");
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if (cause == 8)
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return LOG_STR("Privileged");
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if (cause == 9)
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return LOG_STR("LoadStoreAlignment");
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if (cause == 12)
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return LOG_STR("InstrPDAddrError");
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if (cause == 13)
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return LOG_STR("LoadStorePIFDataError");
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if (cause == 14)
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return LOG_STR("InstrPIFAddrError");
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if (cause == 15)
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return LOG_STR("LoadStorePIFAddrError");
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if (cause == 16)
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return LOG_STR("InstTLBMiss");
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if (cause == 17)
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return LOG_STR("InstTLBMultiHit");
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if (cause == 18)
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return LOG_STR("InstFetchPrivilege");
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if (cause == 20)
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return LOG_STR("InstrFetchProhibited");
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if (cause == 24)
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return LOG_STR("LoadStoreTLBMiss");
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if (cause == 25)
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return LOG_STR("LoadStoreTLBMultihit");
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if (cause == 26)
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return LOG_STR("LoadStorePrivilege");
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if (cause == 28)
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return LOG_STR("LoadProhibited");
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if (cause == 29)
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return LOG_STR("StoreProhibited");
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return nullptr;
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}
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// clang-format off
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PROGMEM_STRING_TABLE(ResetReasonStrings,
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"Unknown", // 0 = fallback
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"Hardware Watchdog", // 1 = REASON_WDT_RST
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"Exception", // 2 = REASON_EXCEPTION_RST
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"Software Watchdog" // 3 = REASON_SOFT_WDT_RST
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);
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// clang-format on
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static_assert(REASON_WDT_RST == 1, "Reset reason enum values must match table indices");
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static_assert(REASON_EXCEPTION_RST == 2, "Reset reason enum values must match table indices");
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static_assert(REASON_SOFT_WDT_RST == 3, "Reset reason enum values must match table indices");
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static const LogString *get_reset_reason(uint32_t reason) {
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return ResetReasonStrings::get_log_str(static_cast<uint8_t>(reason), 0);
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if (reason == REASON_WDT_RST)
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return LOG_STR("Hardware Watchdog");
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if (reason == REASON_EXCEPTION_RST)
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return LOG_STR("Exception");
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if (reason == REASON_SOFT_WDT_RST)
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return LOG_STR("Software Watchdog");
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return LOG_STR("Unknown");
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}
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// Read backtrace from RTC user memory into caller-provided buffer.
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