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esp-idf/tools/test_apps/system/init_array/README.md
Alexey Lapshin 019dc93ae0 feat(esp_system): switch to standard __libc_init_array initialization 
Initially, ESP-IDF used the do_global_ctors() function to run global
constructors. This was done to accommodate Xtensa targets that emit
.ctors.* sections, which are ordered in descending order.

For RISC-V, compilation used .init_array.* sections, which are designed
to have ascending order. Priority constructors in .init_array.* sections
were correctly processed in ascending order. However, non-priority
.init_array section was processed in descending order, as it was done
for Xtensa .ctors.

Starting with ESP-IDF v6.0, the implementation switched to the standard
LibC behavior (__libc_init_array()), which processes both priority and
non-priority constructors in ascending order.

To achieve this, a breaking changes were introduced:
  - Xtensa .ctors.* priority entries converted to .init_array.* format
    (ascending), to be passed to __libc_init_array().
  - Processing order of non-priority .init_array and .ctors sections was
    changed from descending to ascending.

Also, this change introduces .preinit_array for linking. This may be
needed for some C++ or sanitizer features.

Related to https://github.com/espressif/esp-idf/issues/15529
2025-08-04 11:33:44 +08:00

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Supported Targets ESP32 ESP32-C2 ESP32-C3 ESP32-C5 ESP32-C6 ESP32-C61 ESP32-H2 ESP32-H21 ESP32-H4 ESP32-P4 ESP32-S2 ESP32-S3 Linux

Historical note

Initially, ESP-IDF used the do_global_ctors() function to run global constructors. This was done to accommodate Xtensa targets that emit .ctors.* sections, which are ordered in descending order.

For RISC-V, compilation used .init_array.* sections, which are designed to have ascending order. Priority constructors in .init_array.* sections were correctly processed in ascending order. However, non-priority .init_array section was processed in descending order (as it was done for Xtensa .ctors).

Starting with ESP-IDF v6.0, the implementation switched to the standard LibC behavior (__libc_init_array()), which processes both priority and non-priority constructors in ascending order.

To achieve this, a breaking changes were introduced:

  • Xtensa .ctors.* entries converted to .init_array.* format (ascending), to be passed to __libc_init_array().
  • Processing order of non-priority .init_array and .ctors sections was changed from descending to ascending.

This test ensures that the initialization order is correct and consistent between ESP-IDF and Linux targets.