builtin: improve musl/Alpine support (define weak backtrace/backtrace_symbols/backtrace_symbols_fd symbols) (#14250)

vlib/builtin/builtin_backtraces_d_musl.c.v

@@ -0,0 +1,20 @@
+module builtin
+
+// These are just dummy implementations to appease linking on musl/alpine
+
+[export: 'backtrace_symbols']
+[weak]
+fn vbacktrace_symbols(const_buffer &voidptr, size int) &&char {
+	return 0
+}
+
+[export: 'backtrace']
+[weak]
+fn vbacktrace(buffer &voidptr, size int) int {
+	return 0
+}
+
+[export: 'backtrace_symbols_fd']
+[weak]
+fn vbacktrace_symbols_fd(const_buffer &voidptr, size int, fd int) {
+}

vlib/builtin/builtin_backtraces_nix.c.v

@@ -0,0 +1,6 @@
+module builtin
+
+// <execinfo.h>
+fn C.backtrace(a &voidptr, size int) int
+fn C.backtrace_symbols(a &voidptr, size int) &&char
+fn C.backtrace_symbols_fd(a &voidptr, size int, fd int)

vlib/builtin/builtin_d_gcboehm.c.v

@@ -45,10 +45,13 @@ $if dynamic_boehm ? {
 		#flag -DBUS_PAGE_FAULT=T_PAGEFLT
 		#flag -DGC_PTHREADS=1
 		$if !tinyc {
+			#flag -I@VEXEROOT/thirdparty/libgc/include
 			#flag @VEXEROOT/thirdparty/libgc/gc.o
-		} $else {
+		}
+		$if tinyc {
 			#flag -I/usr/local/include
 			#flag $first_existing("/usr/local/lib/libgc.a", "/usr/lib/libgc.a")
+			#flag -lgc
 		}
 		#flag -lpthread
 	} $else $if openbsd {

vlib/builtin/cfns.c.v

@@ -39,13 +39,6 @@ fn C.isdigit(c int) bool
 // stdio.h
 fn C.popen(c &char, t &char) voidptr
 
-// <execinfo.h>
-fn C.backtrace(a &voidptr, size int) int
-
-fn C.backtrace_symbols(a &voidptr, size int) &&char
-
-fn C.backtrace_symbols_fd(a &voidptr, size int, fd int)
-
 // <libproc.h>
 pub fn proc_pidpath(int, voidptr, int) int
 

vlib/v/checker/comptime.v

@@ -564,9 +564,12 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) ComptimeBran
 					'test' {
 						return if c.pref.is_test { .eval } else { .skip }
 					}
+					'musl' {
+						return .unknown
+					}
 					'glibc' {
 						return .unknown
-					} // TODO
+					}
 					'threads' {
 						return if c.table.gostmts > 0 { .eval } else { .skip }
 					}

vlib/v/gen/c/cheaders.v

@@ -366,6 +366,10 @@ const c_common_macros = '
 		#undef VWEAK
 		#define VWEAK
 	#endif
+	#if defined(__MINGW32__) || defined(__MINGW64__)
+		#undef VWEAK
+		#define VWEAK
+	#endif
 #endif
 
 #if !defined(VNORETURN)
@@ -460,11 +464,6 @@ typedef int (*qsort_callback_func)(const void*, const void*);
 	#if defined __has_include
 		#if __has_include (<execinfo.h>)
 			#include <execinfo.h>
-		#else
-			// Most probably musl OR __ANDROID__ ...
-			int backtrace (void **__array, int __size) { return 0; }
-			char **backtrace_symbols (void *const *__array, int __size){ return 0; }
-			void backtrace_symbols_fd (void *const *__array, int __size, int __fd){}
 		#endif
 	#endif
 #endif

vlib/v/gen/c/fn.v

@@ -416,8 +416,9 @@ fn (mut g Gen) gen_fn_decl(node &ast.FnDecl, skip bool) {
 	}
 	for attr in node.attrs {
 		if attr.name == 'export' {
+			weak := if node.attrs.any(it.name == 'weak') { 'VWEAK ' } else { '' }
 			g.writeln('// export alias: $attr.arg -> $name')
-			export_alias := '$type_name $fn_attrs${attr.arg}($arg_str)'
+			export_alias := '$weak$type_name $fn_attrs${attr.arg}($arg_str)'
 			g.definitions.writeln('VV_EXPORTED_SYMBOL $export_alias; // exported fn $node.name')
 			g.writeln('$export_alias {')
 			g.write('\treturn ${name}(')
@@ -2143,6 +2144,10 @@ fn (mut g Gen) write_fn_attrs(attrs []ast.Attr) string {
 				g.write('__NOINLINE ')
 			}
 			'weak' {
+				if attrs.any(it.name == 'export') {
+					// only the exported wrapper should be weak; otherwise x86_64-w64-mingw32-gcc complains
+					continue
+				}
 				// a `[weak]` tag tells the C compiler, that the next declaration will be weak, i.e. when linking,
 				// if there is another declaration of a symbol with the same name (a 'strong' one), it should be
 				// used instead, *without linker errors about duplicate symbols*.

vlib/v/gen/c/testdata/export_and_weak.c.must_have

@@ -0,0 +1,13 @@
+VV_LOCAL_SYMBOL int main__my_other_fn(void);
+VV_EXPORTED_SYMBOL VWEAK int wxyz(void); // exported fn main.my_other_fn
+VWEAK int wxyz(void) {
+VV_LOCAL_SYMBOL int main__my_other_fn(void) {
+
+VV_LOCAL_SYMBOL int main__my_fn(void);
+VV_EXPORTED_SYMBOL int abcd(void); // exported fn main.my_fn
+int abcd(void) {
+VV_LOCAL_SYMBOL int main__my_fn(void) {
+
+	println(int_str(main__my_fn()));
+	println(int_str(main__my_other_fn()));
+

vlib/v/gen/c/testdata/export_and_weak.out

@@ -0,0 +1,2 @@
+42
+11

vlib/v/gen/c/testdata/export_and_weak.vv

@@ -0,0 +1,20 @@
+// This file tests the ability to export functions to C with a fully custom name.
+
+// It also tests, that the exported functions will be exported as weak symbols,
+// if the user tagged them as such.
+
+[export: abcd]
+fn my_fn() int {
+	return 42
+}
+
+[export: wxyz]
+[weak]
+fn my_other_fn() int {
+	return 11
+}
+
+fn main() {
+	println(my_fn())
+	println(my_other_fn())
+}

vlib/v/pref/pref.v

@@ -99,6 +99,8 @@ pub mut:
 	// verbosity           VerboseLevel
 	is_verbose bool
 	// nofmt            bool   // disable vfmt
+	is_glibc          bool // if GLIBC will be linked
+	is_musl           bool // if MUSL will be linked
 	is_test           bool // `v test string_test.v`
 	is_script         bool // single file mode (`v program.v`), main function can be skipped
 	is_vsh            bool // v script (`file.vsh`) file, the `os` module should be made global
@@ -107,17 +109,25 @@ pub mut:
 	is_shared         bool // an ordinary shared library, -shared, no matter if it is live or not
 	is_o              bool // building an .o file
 	is_prof           bool // benchmark every function
+	is_prod           bool // use "-O2"
+	is_repl           bool
+	is_run            bool
+	is_debug          bool // turned on by -g or -cg, it tells v to pass -g to the C backend compiler.
+	is_vlines         bool // turned on by -g (it slows down .tmp.c generation slightly).
+	is_stats          bool // `v -stats file_test.v` will produce more detailed statistics for the tests that were run
+	is_fmt            bool
+	is_vet            bool
+	is_vweb           bool // skip _ var warning in templates
+	is_ios_simulator  bool
+	is_apk            bool     // build as Android .apk format
+	is_help           bool     // -h, -help or --help was passed
+	is_cstrict        bool     // turn on more C warnings; slightly slower
 	test_runner       string   // can be 'simple' (fastest, but much less detailed), 'tap', 'normal'
 	profile_file      string   // the profile results will be stored inside profile_file
 	profile_no_inline bool     // when true, [inline] functions would not be profiled
 	profile_fns       []string // when set, profiling will be off by default, but inside these functions (and what they call) it will be on.
 	translated        bool     // `v translate doom.v` are we running V code translated from C? allow globals, ++ expressions, etc
-	is_prod           bool     // use "-O2"
 	obfuscate         bool     // `v -obf program.v`, renames functions to "f_XXX"
-	is_repl           bool
-	is_run            bool
-	is_debug          bool // turned on by -g or -cg, it tells v to pass -g to the C backend compiler.
-	is_vlines         bool // turned on by -g (it slows down .tmp.c generation slightly).
 	// Note: passing -cg instead of -g will set is_vlines to false and is_debug to true, thus making v generate cleaner C files,
 	// which are sometimes easier to debug / inspect manually than the .tmp.c files by plain -g (when/if v line number generation breaks).
 	sanitize               bool   // use Clang's new "-fsanitize" option
@@ -131,7 +141,6 @@ pub mut:
 	dump_c_flags           string // `-dump-c-flags file.txt` - let V store all C flags, passed to the backend C compiler in `file.txt`, one C flag/value per line.
 	use_cache              bool   // when set, use cached modules to speed up subsequent compilations, at the cost of slower initial ones (while the modules are cached)
 	retry_compilation      bool = true // retry the compilation with another C compiler, if tcc fails.
-	is_stats               bool   // `v -stats file_test.v` will produce more detailed statistics for the tests that were run
 	// TODO Convert this into a []string
 	cflags string // Additional options which will be passed to the C compiler.
 	// For example, passing -cflags -Os will cause the C compiler to optimize the generated binaries for size.
@@ -148,8 +157,6 @@ pub mut:
 	// generating_vh    bool
 	no_builtin       bool   // Skip adding the `builtin` module implicitly. The generated C code may not compile.
 	enable_globals   bool   // allow __global for low level code
-	is_fmt           bool
-	is_vet           bool
 	is_bare          bool   // set by -freestanding
 	bare_builtin_dir string // Set by -bare-builtin-dir xyz/ . The xyz/ module should contain implementations of malloc, memset, etc, that are used by the rest of V's `builtin` module. That option is only useful with -freestanding (i.e. when is_bare is true).
 	no_preludes      bool   // Prevents V from generating preludes in resulting .c files
@@ -162,11 +169,14 @@ pub mut:
 	out_name_c       string // full os.real_path to the generated .tmp.c file; set by builder.
 	out_name         string
 	path             string // Path to file/folder to compile
-	// -d vfmt and -d another=0 for `$if vfmt { will execute }` and `$if another ? { will NOT get here }`
+	//
 	run_only []string // VTEST_ONLY_FN and -run-only accept comma separated glob patterns.
 	// Only test_ functions that match these patterns will be run. -run-only is valid only for _test.v files.
+	//
+	// -d vfmt and -d another=0 for `$if vfmt { will execute }` and `$if another ? { will NOT get here }`
 	compile_defines     []string // just ['vfmt']
 	compile_defines_all []string // contains both: ['vfmt','another']
+	//
 	run_args         []string // `v run x.v 1 2 3` => `1 2 3`
 	printfn_list     []string // a list of generated function names, whose source should be shown, for debugging
 	print_v_files    bool     // when true, just print the list of all parsed .v files then stop.
@@ -178,22 +188,19 @@ pub mut:
 	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=gnu99(linux)/-std=c99 to the C backend
-	use_color           ColorOutput // whether the warnings/errors should use ANSI color escapes.
+	//
-	no_parallel         bool
+	no_parallel       bool // do not use threads when compiling; slower, but more portable and sometimes less buggy
-	is_vweb             bool // skip _ var warning in templates
 	only_check_syntax bool // when true, just parse the files, then stop, before running checker
 	check_only        bool // same as only_check_syntax, but also runs the checker
 	experimental      bool // enable experimental features
 	skip_unused       bool // skip generating C code for functions, that are not used
 	show_timings      bool // show how much time each compiler stage took
-	is_ios_simulator    bool
+	//
-	is_apk              bool     // build as Android .apk format
+	use_color           ColorOutput // whether the warnings/errors should use ANSI color escapes.
 	cleanup_files       []string    // list of temporary *.tmp.c and *.tmp.c.rsp files. Cleaned up on successfull builds.
 	build_options       []string    // list of options, that should be passed down to `build-module`, if needed for -usecache
 	cache_manager       vcache.CacheManager
-	is_help             bool // -h, -help or --help was passed
 	gc_mode             GarbageCollectionMode = .no_gc // .no_gc, .boehm, .boehm_leak, ...
-	is_cstrict          bool                  // turn on more C warnings; slightly slower
 	assert_failure_mode AssertFailureMode     // whether to call abort() or print_backtrace() after an assertion failure
 	message_limit       int = 100 // the maximum amount of warnings/errors/notices that will be accumulated
 	nofloat             bool // for low level code, like kernels: replaces f32 with u32 and f64 with u64
@@ -206,8 +213,25 @@ pub fn parse_args(known_external_commands []string, args []string) (&Preferences
 	return parse_args_and_show_errors(known_external_commands, args, false)
 }
 
+[if linux]
+fn detect_musl(mut res Preferences) {
+	res.is_glibc = true
+	res.is_musl = false
+	if os.exists('/etc/alpine-release') {
+		res.is_musl = true
+		res.is_glibc = false
+		return
+	}
+	my_libs := os.walk_ext('/proc/self/map_files/', '').map(os.real_path(it))
+	if my_libs.any(it.contains('musl')) {
+		res.is_musl = true
+		res.is_glibc = false
+	}
+}
+
 pub fn parse_args_and_show_errors(known_external_commands []string, args []string, show_output bool) (&Preferences, string) {
 	mut res := &Preferences{}
+	detect_musl(mut res)
 	$if x64 {
 		res.m64 = true // follow V model by default
 	}
@@ -412,6 +436,16 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 			'-no-retry-compilation' {
 				res.retry_compilation = false
 			}
+			'-musl' {
+				res.is_musl = true
+				res.is_glibc = false
+				res.build_options << arg
+			}
+			'-glibc' {
+				res.is_musl = false
+				res.is_glibc = true
+				res.build_options << arg
+			}
 			'-no-builtin' {
 				res.no_builtin = true
 				res.build_options << arg
@@ -579,6 +613,10 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 			'-cc' {
 				res.ccompiler = cmdline.option(current_args, '-cc', 'cc')
 				res.build_options << '$arg "$res.ccompiler"'
+				if res.ccompiler == 'musl-gcc' {
+					res.is_musl = true
+					res.is_glibc = false
+				}
 				i++
 			}
 			'-checker-match-exhaustive-cutoff-limit' {