From 7c1fff3495376d135d78eaee8d86df86c6bfe9e2 Mon Sep 17 00:00:00 2001
From: Lance Fredrickson <lancethepants@gmail.com>
Date: Wed, 20 Oct 2021 05:26:25 -0600
Subject: [PATCH] builder: pass `-std=gnu99` to the C backend under linux
 (#12236)

---
 cmd/v/help/build-c.txt | 2 +-
 vlib/v/builder/cc.v    | 6 +++++-
 vlib/v/pref/pref.v     | 2 +-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/cmd/v/help/build-c.txt b/cmd/v/help/build-c.txt
index f4f0f14209..214e9da20c 100644
--- a/cmd/v/help/build-c.txt
+++ b/cmd/v/help/build-c.txt
@@ -243,7 +243,7 @@ see also `v help build`.
       compiler, on the command line, without writing an .rsp file first.
 
    -no-std
-      By default, V passes -std=c99 to the C backend, but some compilers do
+      By default, V passes -std=gnu99(linux)/-std=c99 to the C backend, but some compilers do
       not support that, even though they may be able to compile the produced
       code, or have other options that can be tuned to allow it.
       Passing -no-std will remove that flag, and you can then use -cflags ''
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index 6e7dfc2f83..8fb68ce595 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -162,7 +162,11 @@ fn (mut v Builder) setup_ccompiler_options(ccompiler string) {
 	// arguments for the C compiler
 	ccoptions.args = [v.pref.cflags]
 	if !v.pref.no_std {
-		ccoptions.args << '-std=c99 -D_DEFAULT_SOURCE'
+		if v.pref.os == .linux {
+			ccoptions.args << '-std=gnu99 -D_DEFAULT_SOURCE'
+		} else {
+			ccoptions.args << '-std=c99 -D_DEFAULT_SOURCE'
+		}
 	}
 	ccoptions.wargs = [
 		'-Wall',
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index ebf68cbc0b..6125b7f40b 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -176,7 +176,7 @@ pub mut:
 	fatal_errors        bool        // unconditionally exit after the first error with exit(1)
 	reuse_tmpc          bool        // do not use random names for .tmp.c and .tmp.c.rsp files, and do not remove them
 	no_rsp              bool        // when true, pass C backend options directly on the CLI (do not use `.rsp` files for them, some older C compilers do not support them)
-	no_std              bool        // when true, do not pass -std=c99 to the C backend
+	no_std              bool        // when true, do not pass -std=gnu99(linux)/-std=c99 to the C backend
 	use_color           ColorOutput // whether the warnings/errors should use ANSI color escapes.
 	no_parallel         bool
 	is_vweb             bool // skip _ var warning in templates