JIT: load the GC runtime before the default library

tslang/test/tester/defaultlib-collector.cmake

@@ -6,7 +6,8 @@
 # a user shared library (docs/single-gc-collector-design.md). This drives tslang with the real
 # default library instead:
 #
-#   MODE=jit     the JIT, the program alone and importing a shared library
+#   MODE=jit     the JIT, the program alone and importing a shared library; on Linux also without
+#                the runtime passed in --shared-libs
 #   MODE=compile an exe alone, and an exe importing a shared library that links the default-library DLL
 #
 # The default library is a separate build (TypeScriptCompilerDefaultLib). With none found the test
@@ -131,6 +132,13 @@ if(MODE STREQUAL "jit")
         "${TSLANG}" --emit=jit ${common} "--shared-libs=${runtime}" "${alone}")
     run_program("JIT importing a shared library, default library" "${WORK_DIR}"
         "${TSLANG}" --emit=jit ${common} "--shared-libs=${runtime}" "${program}")
+    # The runtime found by tslang itself (--tslang-lib-path), as a user runs it. On Linux the
+    # default library takes GC_* from the process, so tslang has to load the runtime first; one
+    # passed with --shared-libs is ahead of it anyway, which is why the runs above never failed.
+    if(NOT WIN32)
+        run_program("JIT, default library, runtime not passed" "${WORK_DIR}/alone"
+            "${TSLANG}" --emit=jit ${common} "${alone}")
+    endif()
 elseif(MODE STREQUAL "compile")
     run("--emit=exe alone, default library" "${WORK_DIR}/alone"
         "${TSLANG}" --emit=exe ${common} "${alone}" -o "alone${exe_suffix}")

tslang/tslang/jit.cpp

@@ -593,13 +593,14 @@ static int prepareJitProcess(CompileOptions &compileOptions, bool nativeImage)
     // If shared library implements custom mlir-runner library init and destroy
     // functions, we'll use them to register the library with the execution
     // engine. Otherwise we'll pass library directly to the execution engine.
+    std::string defaultLibFile;
     if (!compileOptions.noDefaultLib && !nativeImage)
     {
         // per-build subfolder (debug/release) must match the JIT compilation mode.
         // Keyed on --di (generate debug info): with debug info use the debug lib.
         // ...and per memory model, for the same reason the linker path is: the default lib
         // allocates the way the model it was built for allocates. See getDefaultLibSubDir.
-        auto defaultLibFile = getDefaultLibBinary(/*shared=*/true, compileOptions,
+        defaultLibFile = getDefaultLibBinary(/*shared=*/true, compileOptions,
                                                   llvm::Triple(llvm::Triple::normalize(llvm::sys::getDefaultTargetTriple()))); // JIT is host-only
 
         // Named here rather than left to the loader, for the reason exe.cpp checks the link
@@ -629,9 +630,7 @@ static int prepareJitProcess(CompileOptions &compileOptions, bool nativeImage)
             return -1;
         }
 #endif
-
-        clSharedLibs.push_back(defaultLibFile);
-    }      
+    }
 
     // add default libs in case they are not part of options
 #ifdef WIN32
@@ -685,6 +684,15 @@ static int prepareJitProcess(CompileOptions &compileOptions, bool nativeImage)
         }
     }
 
+    // After the runtime: on Linux the default library leaves GC_* undefined and takes them from
+    // the process (a collector of its own would be a second one), so they have to be loaded
+    // before it is, or dlopen fails on GC_malloc. A runtime passed with --shared-libs is
+    // already ahead of it.
+    if (!defaultLibFile.empty())
+    {
+        clSharedLibs.push_back(defaultLibFile);
+    }
+
 #ifdef _WIN32
     // tslang.exe links the CRT statically (/MT[d]), so its libc symbols are not in
     // any DLL export table. The JIT's process-symbol resolver would otherwise bind