From 516dbf357fc28c9c199e9a3b1dce72206b770583 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Thu, 27 Jul 2017 18:01:36 -0400
Subject: [PATCH] mark julia threads as initialized

ensures that cfunction can see that Julia state is initialized on this thread

also upgrades the embedding/examples test to handle exceptions better
(e.g. to actually detect them) while testing for correctness

Ref #22987
(cherry picked from commit 98a2d1d5734597c60f436fe3fd78f09ee735a183)
---
 examples/embedding/embedding-test.jl | 16 +++---
 examples/embedding/embedding.c       | 81 +++++++++++++++++++++++-----
 src/threading.c                      |  2 +
 3 files changed, 78 insertions(+), 21 deletions(-)

diff --git a/examples/embedding/embedding-test.jl b/examples/embedding/embedding-test.jl
index 336169085db4c..02f72609507d8 100644
--- a/examples/embedding/embedding-test.jl
+++ b/examples/embedding/embedding-test.jl
@@ -4,17 +4,19 @@
 using Base.Test
 
 @test length(ARGS) == 1
-let
+@testset "embedding example" begin
     stdout = Pipe()
     stderr = Pipe()
     p = spawn(pipeline(Cmd(ARGS), stdin=DevNull, stdout=stdout, stderr=stderr))
     close(stdout.in)
     close(stderr.in)
-    stderr_task = @async readlines(stderr)
-    lines = readlines(stdout)
-    @test length(lines) == 6
-    @test parse(Float64, lines[1]) ≈ sqrt(2)
-    lines = wait(stderr_task)
-    @test lines == ["UndefVarError(:this_function_does_not_exist)"]
+    stdout_task = @async readlines(stdout)
+    stderr = read(stderr, String)
+    @test stderr == "MethodError: no method matching this_function_has_no_methods()\n"
     @test success(p)
+    lines = wait(stdout_task)
+    @test length(lines) == 9
+    @test parse(Float64, lines[1]) ≈ sqrt(2)
+    @test lines[8] == "called bar"
+    @test lines[9] == "calling new bar"
 end
diff --git a/examples/embedding/embedding.c b/examples/embedding/embedding.c
index 5bb70aadc04c2..a4172a1b18583 100644
--- a/examples/embedding/embedding.c
+++ b/examples/embedding/embedding.c
@@ -12,22 +12,39 @@ double my_c_sqrt(double x)
     return sqrt(x);
 }
 
+jl_value_t *checked_eval_string(const char* code)
+{
+    jl_value_t *result = jl_eval_string(code);
+    if (jl_exception_occurred()) {
+        // none of these allocate, so a gc-root (JL_GC_PUSH) is not necessary
+        jl_call2(jl_get_function(jl_base_module, "showerror"),
+                 jl_stderr_obj(),
+                 jl_exception_occurred());
+        jl_printf(jl_stderr_stream(), "\n");
+        jl_atexit_hook(1);
+        exit(1);
+    }
+    assert(result && "Missing return value but no exception occurred!");
+    return result;
+}
+
 int main()
 {
     jl_init();
 
     {
-        // Simple running Julia code
+        // Simple running of Julia code
 
-        jl_eval_string("println(sqrt(2.0))");
+        checked_eval_string("println(sqrt(2.0))");
     }
 
     {
         // Accessing the return value
 
-        jl_value_t *ret = jl_eval_string("sqrt(2.0)");
+        jl_value_t *ret = checked_eval_string("sqrt(2.0)");
         double retDouble = jl_unbox_float64(ret);
         printf("sqrt(2.0) in C: %e\n", retDouble);
+        fflush(stdout);
     }
 
     {
@@ -38,62 +55,98 @@ int main()
         jl_value_t* ret = jl_call1(func, argument);
         double retDouble = jl_unbox_float64(ret);
         printf("sqrt(2.0) in C: %e\n", retDouble);
+        fflush(stdout);
     }
 
     {
         // 1D arrays
 
-        jl_value_t* array_type = jl_apply_array_type( (jl_value_t*)jl_float64_type, 1 );
-        jl_array_t* x          = jl_alloc_array_1d(array_type , 10);
+        jl_value_t* array_type = jl_apply_array_type((jl_value_t*)jl_float64_type, 1);
+        jl_array_t* x          = jl_alloc_array_1d(array_type, 10);
+        // JL_GC_PUSH* is required here to ensure that `x` is not deleted before
+        // (aka, is gc-rooted until) the program reaches the corresponding JL_GC_POP()
         JL_GC_PUSH1(&x);
 
         double* xData = jl_array_data(x);
 
         size_t i;
-        for(i=0; i<jl_array_len(x); i++)
+        for (i = 0; i < jl_array_len(x); i++)
             xData[i] = i;
 
         jl_function_t *func  = jl_get_function(jl_base_module, "reverse!");
         jl_call1(func, (jl_value_t*) x);
 
         printf("x = [");
-        for(i=0; i<jl_array_len(x); i++)
+        for (i = 0; i < jl_array_len(x); i++)
             printf("%e ", xData[i]);
         printf("]\n");
+        fflush(stdout);
 
         JL_GC_POP();
     }
 
     {
-        // define julia function and call it
+        // Defining a Julia function and calling it
 
-        jl_eval_string("my_func(x) = 2*x");
+        checked_eval_string("my_func(x) = 2 * x");
 
         jl_function_t *func = jl_get_function(jl_current_module, "my_func");
         jl_value_t* arg = jl_box_float64(5.0);
         double ret = jl_unbox_float64(jl_call1(func, arg));
 
         printf("my_func(5.0) = %f\n", ret);
+        fflush(stdout);
     }
 
     {
-        // call c function
+        // Calling a C function from Julia (from C)
 
-        jl_eval_string("println( ccall( :my_c_sqrt, Float64, (Float64,), 2.0 ) )");
+        // in a shared library (exported, by name)
+        checked_eval_string("println( ccall(:my_c_sqrt, Float64, (Float64,), 2.0) )");
+
+        // or via a pointer
+        jl_value_t *call_by_ptr = checked_eval_string(
+                "my_c_sqrt -> println( ccall(my_c_sqrt, Float64, (Float64,), 2.0) )");
+        jl_call1(call_by_ptr, jl_box_voidpointer(my_c_sqrt));
     }
 
     {
-        // check for exceptions
+        // Handling exceptions gracefully
 
-        jl_eval_string("this_function_does_not_exist()");
+        jl_value_t *f = checked_eval_string("function this_function_has_no_methods end");
+        jl_call0(f);
 
         if (jl_exception_occurred()) {
-            jl_call2(jl_get_function(jl_base_module, "show"), jl_stderr_obj(), jl_exception_occurred());
+            jl_call2(jl_get_function(jl_base_module, "showerror"),
+                     jl_stderr_obj(),
+                     jl_exception_occurred());
             jl_printf(jl_stderr_stream(), "\n");
         }
 
     }
 
+    {
+        // Creating and using a native C function handle
+        // to a Julia function signature
+
+        checked_eval_string(
+                "function bar()\n"
+                "    println(\"called bar\")\n"
+                "    random_return_value = 42\n"
+                "end");
+        checked_eval_string(
+                "function bar_from_c()\n"
+                "    bar()\n"
+                "    nothing\n"
+                "end");
+        typedef void (*Func_VOID__VOID)(void);
+        jl_value_t *pbar = jl_eval_string("cfunction(bar_from_c, Void, ())");
+        Func_VOID__VOID bar = (Func_VOID__VOID)jl_unbox_voidpointer(pbar);
+        bar();
+        checked_eval_string("bar() = println(\"calling new bar\")");
+        bar();
+    }
+
     int ret = 0;
     jl_atexit_hook(ret);
     return ret;
diff --git a/src/threading.c b/src/threading.c
index abf183ae3576d..c9958f9e69b03 100644
--- a/src/threading.c
+++ b/src/threading.c
@@ -263,6 +263,8 @@ static void ti_initthread(int16_t tid)
 #ifndef _OS_WINDOWS_
     ptls->system_id = pthread_self();
 #endif
+    assert(ptls->world_age == 0);
+    ptls->world_age = 1; // OK to run Julia code on this thread
     ptls->tid = tid;
     ptls->pgcstack = NULL;
     ptls->gc_state = 0; // GC unsafe