[franz-hoepfinger-4diac]

Description

C++ ELF applications loaded by elf_loader never had their static constructors executed, because .preinit_array / .init_array / .fini_array were ignored.

This PR:

• records the three arrays after relocation (esp_elf_find_init_arrays()); in section mode (ESP32/S2/S3) it now also copies them to memory, because otherwise relocations that target them have no destination, and it handles the legacy .ctors/.dtors layout the Xtensa toolchain emits (.ctors runs backwards),
• runs .preinit_array and .init_array once, in order, before the entry point in esp_elf_request(),
• runs .fini_array in reverse order in esp_elf_deinit() (only if the constructors were run),
• documents C++ ELF applications in the README (the host has to register C++ runtime symbols such as operator new/delete and __cxa_pure_virtual with esp_elf_register_symbol(); __dso_handle / __cxa_atexit must live in the ELF or be exported by the host) and adds a CHANGELOG entry.

Fixes #796

Testing

Tested on ESP32-S31 (RISC-V) and ESP32-S3 (Xtensa), ESP-IDF v6.1, with elf_console_example-style host (ELF on LittleFS, exec shell command). The test ELF has a class hierarchy with virtual functions, new/delete, a global object with constructor/destructor, and __attribute__((constructor(101))) / __attribute__((destructor)) functions. Same output on both targets:

early_ctor (init_array, priority 101)
Global Counter ctor (init_array ran)
s_counter.next() = 42 (expected 42 if constructor ran)
Shape ctor: Rect
Rect area = 12 (expected 12)
Shape ctor: Rect
Rect area = 25 (expected 25)
Shape dtor: Rect
C++ test done
Global Counter dtor
Shape dtor: Rect
Success to exit from ELF file
late_dtor (fini_array)

Not tested: ESP32 / ESP32-S2 (same code path as ESP32-S3), the dynamic shared object (dlopen) path, .preinit_array, C++ exceptions and RTTI.

Checklist

• Tested on hardware (ESP32-S31, ESP32-S3)
• CHANGELOG and README updated

🤖 Generated with Claude Code

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[wujiangang]

Thanks for the contribution. The C++ constructor/destructor support was brought into master in 028dcf7, then adapted for elf_loader v2.0.0 in 3a6a02e. The functionality is already included, so I'm closing this PR to avoid applying it twice.