Fix tool/library memory management/mixup issues

[bagder]

memory allocated by libcurl must be freed with curl_free(),

memory allocated by the tool itself must be freed with curlx_free().

[Copilot]

Pull request overview

This PR aims to prevent allocator “mixups” between libcurl-owned memory (must be freed with curl_free()) and tool-owned memory (must be freed with curlx_free()), and introduces an opt-in debug mode to help detect such mistakes.

Changes:

• Fix several mismatched curl_free()/curlx_free() call sites and normalize ownership transfers (dup into tool memory when needed).
• Add --enable-init-mem-debug / CURL_DEBUG_GLOBAL_MEM mode to run the curl tool using curl_global_init_mem() with custom allocators and expose this in curl -V.
• Add a new CI job to exercise the debug mode under valgrind.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/runtests.pl	Tightens Debug feature detection to avoid accidental matches from new “global-mem-debug” wording.
src/var.c	Frees base64-encoded/decoded buffers with curlx_free() (tool allocator), not curl_free().
src/tool_operhlp.c	Uses curl_free() for libcurl-allocated strings and transfers URL ownership into tool memory.
src/tool_operate.c	Ensures URL/header/outfile strings end up tool-owned when later freed by tool helpers.
src/tool_help.c	Adds “global-mem-debug” to the tool’s feature list when enabled.
src/tool_cfgable.c	Adds debug-only curl_global_init_mem() wiring with custom allocators.
src/tool_cb_hdr.c	Avoids curl_maprintf for header cloning; uses curlx_memdup0 and tool frees.
lib/curlx/dynbuf.c	Frees curl_mvaprintf() output with curl_free() (libcurl allocator).
configure.ac	Adds --enable-init-mem-debug and defines CURL_DEBUG_GLOBAL_MEM.
CMakeLists.txt	Introduces a CMake option for the feature (currently not wired into compilation).
.github/workflows/linux.yml	Adds a valgrind CI job enabling the new init-mem debug mode.

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[bagder]

augment review

[augmentcode]

🤖 Augment PR Summary

Summary: This PR tightens separation between tool-owned allocations and libcurl-owned allocations, aiming to prevent (and actively detect) mismatched free calls.

Changes:

• Adjust several call sites to free libcurl-allocated strings with curl_free() and tool-allocated strings with curlx_free()/tool_safefree().
• When APIs return libcurl-allocated buffers (e.g., URL API, maprintf helpers), duplicate into tool memory where needed and release the original with curl_free().
• Add an optional debug build mode that initializes libcurl via curl_global_init_mem() with custom allocators (CURL_DEBUG_GLOBAL_MEM / --enable-init-mem-debug) to flush out mixups.
• Extend curl -V feature output to advertise the new "global-mem-debug" marker when enabled.
• Update the test harness feature parsing to avoid falsely detecting Debug builds due to the new "global-mem-debug" feature name.
• Add a CI job running this mode under valgrind to catch allocator/free mismatches.

Technical Notes: The added mode is intended for diagnostics and depends on using a shared libcurl (per the new in-code notes).

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[augmentcode]

Review completed. 2 suggestions posted.

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