Compile a source beside its inline-mocked header from an isolated copy

[mkarlesky]

Fixes :cmock ↳ :treat_inlines: :include for sources that share a directory with the header their test mocks. That is a very common layout: a source and its headers together in src/. In it, the source under test still ran the real inline bodies instead of the mock, and a hardware-touching inline could crash the test. The fault-injection stress rig found this in its own first fixture. It may also be the crash reported in #1240.

Cause

C's #include "..." checks the including file's own directory before any -I path. Under :treat_inlines: :include, CMock writes an inline-stripped copy of each mocked header into the mocks directory, first on the search path. A source beside the real header never consults that path, so #include "board.h" in src/gpio.c finds src/board.h directly.

Ceedling already handles this rule for headers. isolate_sibling_headers stages a sibling header that a test file's compile reaches. The source under test is not a header, and it never appears in the test file's .d file, so nothing redirected it.

Fix

A qualifying source compiles from a copy staged alone in a throwaway directory. With no real header beside the copy, its #include reaches CMock's stripped copy through the search path. The decision is made up front: mocks enabled, :treat_inlines: :include, a real-header mock rather than a Partial mock, a source other than the test file, the same directory as the mocked header, and a quoted #include of that header by name.

Four details keep the copy invisible to everything but header lookup:

• #line 1 "<original path>" opens the copy. Diagnostics, __FILE__, debug info and coverage all name the original at its original line numbers. Verified with gcov: the report reads File 'src/reader.c', and gcovr's report is unaffected.
• The original's directory is appended after every other search path. The source's other quoted and relative includes still resolve, and the mocks directory keeps precedence.
• The .d file is rewritten to name the original before registration. Dependency tracking never records a file that disappears once the compile ends, so a second build skips the object as usual.
• Plugins and logs keep the original path. Generator#generate_object_file_c gains compile_source: for the command line. arg_hash[:source], which compile_commands_json_db, Bullseye, gcov and command_hooks read, is unchanged.

Each staging lives for one compile and writes nothing to the testable, so it never touches the two-pass barrier in stage_build_objects.

Consolidation

Staging a file away from its neighbors already happened in two places, and this fix needed a third. The first commit extracts QuoteIncludeIsolator (lib/ceedling/quote_include_isolator.rb) with no change in behavior. It owns staging, scoped release, mapping a copy's path back to its original, the optional #line directive, and the include-by-name scan. Bare-includes extraction and sibling-header isolation move onto it, replacing FileWrapper#stage_isolated_copies and #remove_isolated_copies and the executor's private scan. The second commit is the fix, built on the isolator. Each commit passes the full unit and integration tiers on its own.

Changes

• lib/ceedling/quote_include_isolator.rb: new, wired in lib/ceedling/objects.yml.
• lib/ceedling/test_invoker/test_build_executor.rb: inline_mocked_sibling_header decides isolation, and compile_isolated_source compiles the copy. Sibling-header isolation now stages through the isolator.
• lib/ceedling/preprocess/preprocessinator_includes_handler.rb: bare-includes extraction stages through QuoteIncludeIsolator#within.
• lib/ceedling/generators/generator.rb: compile_source:.
• lib/ceedling/file_wrapper.rb: the two staging methods are removed.
• lib/ceedling/test_invoker/HEADER_COLLISIONS.md, lib/ceedling/preprocess/README.md: the isolator as the mechanism's single home, plus a new section on sources under test.

Tests

• spec/units/quote_include_isolator_spec.rb, new: staging, release on raise, #line escaping for Windows paths, path restoration in plain, make-escaped and binary text, and the include scan.
• spec/integration/quote_include_isolator_spec.rb, renamed from file_wrapper_isolated_copies_spec.rb: real files plus a real gcc compile of a staged copy. It reaches a shadow header ahead of the real one beside the original, resolves the original's other includes, reports the original as __FILE__, and leaves a dependency file free of the copy.
• spec/units/test_build_executor_spec.rb: the isolated compile, .d restoration before registration and on failure, the notice, unchanged staleness meta, and an ordinary compile for each non-qualifying case.
• spec/units/generators/generator_spec.rb, new: the command line receives compile_source while plugin hooks receive :source.
• spec/system/sibling_header_collision_spec.rb: a source beside a crash-on-purpose inline header passes, and a second build leaves the object fresh. Without the fix, the same test segfaults.

The existing executor and includes-handler specs now use the isolator in place of the FileWrapper staging stubs. Units pass 3992/0 and integration 298/0, along with the include-handling, preprocessing, Partials and gcov system specs.

Not verified

Bullseye could not be run here. Its covc wraps the real command line, so whether its coverage data names the copy or follows #line is unconfirmed. A source reaching the real header only through a private header of its own is not redirected. That is the same one-level limit sibling-header isolation documents.