From dc00f0d65a2ee7049d386d7c3e98e540dbc243b9 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 30 Apr 2026 03:07:28 +0300
Subject: [PATCH] builder: fix TCC compiler integration for parallel
 compilation (#27033)

---
 vlib/v/builder/cbuilder/parallel_cc.v | 22 ++++++++++++++++------
 vlib/v/gen/c/cgen.v                   |  8 ++------
 vlib/v/gen/c/cheaders.v               |  6 +++++-
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/vlib/v/builder/cbuilder/parallel_cc.v b/vlib/v/builder/cbuilder/parallel_cc.v
index 6d200839a..c6a2ff4f2 100644
--- a/vlib/v/builder/cbuilder/parallel_cc.v
+++ b/vlib/v/builder/cbuilder/parallel_cc.v
@@ -80,11 +80,18 @@ fn parallel_cc(mut b builder.Builder, result c.GenOutput) ! {
 	mut compile_args := b.get_compile_args()
 	mut linker_args := b.get_linker_args()
 	if b.ccoptions.cc == .tcc {
-		tcc_root := os.join_path(@VEXEROOT, 'thirdparty', 'tcc')
-		if os.is_dir(tcc_root) {
-			tcc_base_arg := '-B${b.tcc_quoted_path(tcc_root)}'
-			compile_args << tcc_base_arg
-			linker_args << tcc_base_arg
+		// vlang/tcc has its system headers under `${vroot}/thirdparty/tcc/lib/tcc/include/`
+		// and its runtime objects (libtcc1.a, bt-*.o) under `${vroot}/thirdparty/tcc/lib/tcc/`.
+		// `-B` controls tcc's include search (`${B}/include`) and `-L` adds a library search path,
+		// so pass absolute paths for both. This lets tcc find them regardless of the cwd from
+		// which v was invoked, without affecting how user-supplied relative flags are resolved.
+		tcc_install_dir := os.join_path(@VEXEROOT, 'thirdparty', 'tcc', 'lib', 'tcc')
+		if os.is_dir(tcc_install_dir) {
+			tcc_b_arg := '-B${b.tcc_quoted_path(tcc_install_dir)}'
+			tcc_l_arg := '-L${b.tcc_quoted_path(tcc_install_dir)}'
+			compile_args << tcc_b_arg
+			linker_args << tcc_b_arg
+			linker_args << tcc_l_arg
 		}
 	}
 	scompile_args := compile_args.join(' ')
@@ -138,7 +145,10 @@ fn parallel_cc(mut b builder.Builder, result c.GenOutput) ! {
 	sw_link := time.new_stopwatch()
 	link_res := os.execute(link_cmd)
 	eprint_result_time(sw_link, 'link_cmd', link_cmd, link_res)
-	if link_res.exit_code != 0 {
+	// tcc reports duplicate symbol errors via stderr and an executable still gets emitted with exit code 0,
+	// so detect that pattern and treat it as a link failure too.
+	link_failed_with_tcc_dup := b.ccoptions.cc == .tcc && link_res.output.contains('defined twice')
+	if link_res.exit_code != 0 || link_failed_with_tcc_dup {
 		return error_with_code('failed to link after parallel C compilation', 1)
 	}
 }
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 0d0234782..f2f3cc46f 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -13031,9 +13031,7 @@ fn (mut g Gen) panic_debug_info(pos token.Pos) (int, string, string, string) {
 // when available, or emits `imessage` through a C error otherwise.
 pub fn get_guarded_include_text(iname string, imessage string) string {
 	res := '
-	|#if defined(__TINYC__)
-	|#include ${iname}
-	|#elif defined(__has_include)
+	|#if defined(__has_include)
 	|#if __has_include(${iname})
 	|#include ${iname}
 	|#else
@@ -13050,9 +13048,7 @@ pub fn get_guarded_include_text(iname string, imessage string) string {
 // the best available integer types header, or emits `imessage` otherwise.
 pub fn get_inttypes_or_stdint_include_text(imessage string) string {
 	res := '
-	|#if defined(__TINYC__)
-	|#include <stdint.h>
-	|#elif defined(__has_include)
+	|#if defined(__has_include)
 	|#if __has_include(<inttypes.h>)
 	|#include <inttypes.h>
 	|#elif __has_include(<stdint.h>)
diff --git a/vlib/v/gen/c/cheaders.v b/vlib/v/gen/c/cheaders.v
index 99f1d3f8a..e565dadce 100644
--- a/vlib/v/gen/c/cheaders.v
+++ b/vlib/v/gen/c/cheaders.v
@@ -214,7 +214,11 @@ const c_common_macros = '
 		#endif
 	#else
 		#define VV_EXP extern
-		#define VV_LOC static
+		#ifdef _VPARALLELCC
+			#define VV_LOC
+		#else
+			#define VV_LOC static
+		#endif
 	#endif
 #endif
 #ifdef __cplusplus
-- 
2.39.5