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base repository: etr/libhttpserver
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compare: fix/issue-375-null-key-post-iterator
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  • 4 commits
  • 4 files changed
  • 2 contributors

Commits on Jun 29, 2026

  1. Fix null key dereference in post_iterator (#375) 

    MHD may invoke the post iterator with a null key on a continuation
chunk (off > 0): the field name is supplied only on the first call and
not repeated. The no-file branch passed the raw key pointer into
std::string (via grow_last_arg / set_arg), which throws std::logic_error
on null. Because the throw escapes the C post-iterator callback, it
propagates as an uncaught exception and aborts the process via
std::terminate.

Guard key for null before constructing std::string: with no field name
there is nothing to store the value under, so accept and silently skip
the chunk (MHD_YES keeps the request alive; MHD_NO would abort it).
Same class of bug as the null-uri fix in uri_log (#371).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rkuh4aSmrD8m2f2vYqakb6
    @etr @claude
    etr and claude committed Jun 29, 2026
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  2. Add ChangeLog entry for #375 fix 

    Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rkuh4aSmrD8m2f2vYqakb6
    @etr @claude
    etr and claude committed Jun 29, 2026
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  3. Add regression unit test for null key in post_iterator (#375) 

    White-box unit test that drives webserver::post_iterator directly with a
null key on both the continuation (off > 0) and initial chunks. Without
the guard the test process terminates (std::logic_error from
std::string(nullptr) escaping the callback); with it the chunk is
accepted and skipped. Adds happy-path coverage (initial store and
large-field continuation append) to pin that the guard does not regress
normal form handling.

post_iterator and http_request's constructor / setters are private, so
the test uses the standard private->public white-box include technique
(standard + libmicrohttpd headers are pulled in first so only
libhttpserver's own declarations are affected; member order is
unchanged, so object layout matches the normally-compiled library).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rkuh4aSmrD8m2f2vYqakb6
    @etr @claude
    etr and claude committed Jun 29, 2026
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  4. Make post_iterator null-key test portable across stdlibs (#375) 

    The first version of the test used `#define private public` to reach the
private static webserver::post_iterator. That breaks libstdc++'s
<sstream> (struct __xfer_bufptrs redeclared with different access) when it
is pulled in transitively under the redefined keyword, failing the Linux
CI build while passing on macOS/libc++.

Replace it with the explicit-instantiation access loophole: access checks
do not apply to names used in an explicit template instantiation, so a
filler<> whose static member runs at dynamic-init time captures a pointer
to post_iterator without redefining any keyword or touching a shipped
header. Portable across libstdc++ and libc++.

Drop the http_request-backed happy-path cases (still covered by the
file_upload integration test's 192 checks) and assert the two null-key
paths return MHD_YES without throwing; dhr is left null since a correct
guard returns before any dhr access.

Verified: clean under -Wall -Wextra -Werror -pedantic and cpplint; the
test still terminates without the guard and passes with it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rkuh4aSmrD8m2f2vYqakb6
    @etr @claude
    etr and claude committed Jun 29, 2026
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