[finger563]

Summary

Fixes #854. NvsHandle::get() for std::string sized the string with get_item_size(), which for strings counts the zero terminator (IDF documents this on get_item_size), and get_string() then wrote that terminator into the string. A stored "ABCDEFG" came back with size() == 8 and a trailing '\0', so == / compare() failed and serialised output carried an embedded NUL, exactly as reported.

The change is confined to the two std::string read overloads in nvs_handle_espp.hpp (get(key, std::string&, ec) and get(key, std::string&, default, ec), which Nvs::get_var / get_or_set_var dispatch to): after a successful get_string() the string is resized to len - 1, so size() is the stored string's length. The generic / bool / float paths and the string write path are untouched; the default-value branch still assigns the default unchanged. The doc comments say what size() now means, and the example prints the size next to each string it reads back.

Example validation section

The nvs example now ends with a self-check section (//! [nvs validation]) that exercises the NVS operations with explicit pass / fail checks and prints a summary (NVS validation: 18/18 checks passed - PASS, failing checks listed after it). It runs in its own validate namespace that is erased before and after, so every boot runs the same sequence:

• integer / bool / float round trips through get_or_set_var (missing key stores and returns the default) and set_var / get_var
• strings: default on a missing key, stored value on an existing key, round trip with exact size() and last character, shorter overwrite into a longer destination, empty string, 64-character string, strlen(c_str()) == size(), no embedded '\0'
• erase key (key gone, others survive), read of a missing key fails and leaves the value alone, erase namespace (all keys gone)

The string checks are the regression test for #854: before the fix, size() is one too large and the equality checks fail.

Test plan

• components/nvs/example builds for esp32 (IDF 6.1) and esp32p4
• On hardware: the example prints String = 'default' (7 bytes) on first boot and String = 'hello' (5 bytes) after the set; the reporter's test_NVS() prints size=7 for both reads
• On hardware: the validation section prints NVS validation: 18/18 checks passed - PASS

🤖 Generated with Claude Code

https://claude.ai/code/session_01DFjjnq3XCTRAXENSxsCxJU

[github-actions]

✅Static analysis result - no issues found! ✅