Segmentation Fault in std.array when calling InPlaceAppender.ensureAddable(size_t nelems)

[andrewlalis]

When running my program with gdb, I get the following segmentation fault:

Thread 16 "http1-test" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffcd7fa640 (LWP 33330)]
0x000055555576899b in _D3std5array__T15InPlaceAppenderTAyaZQw13ensureAddableMFNaNbNfmZv (this=..., nelems=0) at /usr/include/dmd/phobos/std/array.d:3842
3842        private void ensureAddable(size_t nelems)
(gdb) display nelems
1: nelems = 0

I don't know exactly what's happening, because the segmentation fault is being thrown as soon as this line is called:

auto headerStr = consumeUntil(inputStream, "\r\n");

where consumeUntil is defined as

/**
 * Helper function to consume string content from an input stream until a
 * certain target pattern of characters is encountered.
 * Params:
 *   inputStream = The stream to read from.
 *   target = The target at which to stop reading.
 * Returns: The string that was read, or a stream error.
 */
Either!(string, "value", StreamError, "error") consumeUntil(S)(
    S inputStream,
    string target
) if (isByteInputStream!S) {
    ubyte[1024] buffer;
    size_t idx;
    while (true) {
        auto result = inputStream.readFromStream(buffer[idx .. idx + 1]);
        if (result.hasError) return Either!(string, "value", StreamError, "error")(result.error);
        if (result.count != 1) return Either!(string, "value", StreamError, "error")(
            StreamError("Failed to read a single element", 1)
        );
        idx++;
        if (idx >= target.length && buffer[idx - target.length .. idx] == target) {
            return Either!(string, "value", StreamError, "error")(
                cast(string) buffer[0 .. idx - target.length].idup
            );
        }
        if (idx >= buffer.length) {
            return Either!(string, "value", StreamError, "error")(
                StreamError("Couldn't find target \"" ~ target ~ "\" after reading 1024 bytes.", 1)
            );
        }
    }
}

and ultimately, inputStream.readFromStream is calling BufferedInputStream.readFromStream.

[andrewlalis]

Note that I've checked and confirmed that no code inside of consumeUntil is being executed. The segmentation fault is thrown simply by attempting to call the function.