pref: add support for `-thread-stack-size 4194304` (default set to 8MB) (#14168)

cmd/v/help/build-c.txt

@@ -257,7 +257,7 @@ see also `v help build`.
       Passing -no-std will remove that flag, and you can then use -cflags ''
       to pass the other options for your specific C compiler.
 
--assert aborts
+   -assert aborts
       Call abort() after an assertion failure. Debuggers usually
       install signal handlers for SIGABRT, so your program will stop and you
       will get a backtrace. If you are running your program outside of a
@@ -267,3 +267,14 @@ see also `v help build`.
       Call print_backtrace() after an assertion failure. Note that
       backtraces are not implemented yet on all combinations of
       platform/compiler.
+
+   -thread-stack-size 4194304
+      Set the thread stack size to 4MB. Use multiples of 4096.
+      The default is 8MB, which is enough for compiling V programs, with deeply
+      nested expressions (~40 levels).
+      It may need to be increased, if you are getting stack overflow errors for
+      deeply recursive programs like some of the stages of the V compiler itself,
+      that use relatively few threads.
+      It may be decreased, to reduce the memory footprint of programs that launch
+      hundreds/thousands of threads, but where each of the threads does not need
+      a big stack.

vlib/v/gen/c/fn.v

@@ -1777,7 +1777,14 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 		}
 	} else {
 		g.writeln('pthread_t thread_$tmp;')
-		g.writeln('int ${tmp}_thr_res = pthread_create(&thread_$tmp, NULL, (void*)$wrapper_fn_name, $arg_tmp_var);')
+		mut sthread_attributes := 'NULL'
+		if g.pref.os != .vinix {
+			g.writeln('pthread_attr_t thread_${tmp}_attributes;')
+			g.writeln('pthread_attr_init(&thread_${tmp}_attributes);')
+			g.writeln('pthread_attr_setstacksize(&thread_${tmp}_attributes, $g.pref.thread_stack_size);')
+			sthread_attributes = '&thread_${tmp}_attributes'
+		}
+		g.writeln('int ${tmp}_thr_res = pthread_create(&thread_$tmp, $sthread_attributes, (void*)$wrapper_fn_name, $arg_tmp_var);')
 		g.writeln('if (${tmp}_thr_res) panic_error_number(tos3("`go ${name}()`: "), ${tmp}_thr_res);')
 		if !node.is_expr {
 			g.writeln('pthread_detach(thread_$tmp);')

vlib/v/pref/pref.v

@@ -199,6 +199,7 @@ pub mut:
 	nofloat             bool              // for low level code, like kernels: replaces f32 with u32 and f64 with u64
 	// checker settings:
 	checker_match_exhaustive_cutoff_limit int = 12
+	thread_stack_size                     int = 8388608 // Change with `-thread-stack-size 4194304`. Note: on macos it was 524288, which is too small for more complex programs with many nested callexprs.
 }
 
 pub fn parse_args(known_external_commands []string, args []string) (&Preferences, string) {
@@ -571,6 +572,10 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 				res.message_limit = cmdline.option(current_args, arg, '5').int()
 				i++
 			}
+			'-thread-stack-size' {
+				res.thread_stack_size = cmdline.option(current_args, arg, res.thread_stack_size.str()).int()
+				i++
+			}
 			'-cc' {
 				res.ccompiler = cmdline.option(current_args, '-cc', 'cc')
 				res.build_options << '$arg "$res.ccompiler"'

vlib/v/tests/default_thread_stack_size_test.v

@@ -0,0 +1,26 @@
+fn f(x u8) u8 {
+	eprintln('> f: $x')
+	if x == 0 {
+		return 0
+	}
+	mut local := [131072]u8{}
+	local[local.len - 1] = x + f(x - 1)
+	return local[0] + local[local.len - 1]
+}
+
+fn abc(depth u8) u8 {
+	return f(depth)
+}
+
+fn test_default_stack_depth() {
+	$if tinyc && windows {
+		exit(0) // skip for now testing on windows-tcc
+	}
+	// Note: 10 levels of recursing f, requires a little over 1.4MB,
+	// and would have failed on macos, where the default thread size
+	// is just 512KB, if V was not changed to have a default for
+	// `-thread-stack-size` of 8MB.
+	t := go abc(10)
+	res := t.wait()
+	assert res == 55
+}