[fix] Reading from stdin was effectively broken

Introduced in 582d6f7 because of dumb
copy-paste error.

.github/workflows/test-cpp.yml

@@ -238,6 +238,8 @@ jobs:
         mkdir -p "build-sanitized-$sanitizer" && cd -- "$_"
         CXX=clang++ CC=clang cmake -G Ninja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="-fsanitize=$sanitizer -DSHORT_TESTS" ..
         cmake --build . -- check
+        cmake --build .
+        bash ../src/tests/testRapidgzip.sh
 
   UBSan:
     name: UBSan

src/core/filereader/SinglePass.hpp

@@ -236,7 +236,6 @@ class SinglePassFileReader final :
             if ( underlyingSize && ( m_file->seekable() || ( *underlyingSize > 0 ) ) ) {
                 return *underlyingSize;
             }
-            return m_fileno;
         }
         return std::nullopt;
     }

src/tests/testRapidgzip.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+# Should be run from build folder
+
+
+RAPIDGZIP='src/tools/rapidgzip'
+export RAPIDGZIP
+
+function echoerr() { echo "$@" 1>&2; }
+
+returnError()
+{
+    local lineNumber message
+    if [ $# -eq 2 ]; then
+        lineNumber=:$1
+        message=$2
+    else
+        message=$*
+    fi
+
+    echoerr -e "\e[37m${FUNCNAME[1]}$lineNumber <- ${FUNCNAME[*]:2}\e[0m"
+    echoerr -e "\e[37m$message\e[0m"
+    echoerr -e '\e[31mTEST FAILED!\e[0m'
+
+    exit 1
+}
+
+
+# Tests with stdin are hard to do in Catch2, so do them here.
+[[ "$( cat ../src/tests/data/base64-256KiB.gz | $RAPIDGZIP --count )" -eq 262144 ]] ||
+    returnError "$LINENO" 'Stdin count test failed!'
+
+echo -e '\e[32mAll tests ran successfully.\e[0m'