all: support `-gc boehm` on systems with libgc-dev installed (#9382)

cmd/v/help/build-c.txt

@@ -70,6 +70,20 @@ see also `v help build`.
       Some short lived applications, like compilers and other CLI tools are
       more performant without autofree.
       
+   -gc <mode>
+      Use and link an optional garbage collector. 
+      Only `-gc boehm` is supported currently. You need to install a
+      `libgc-dev` package first, or install it manually from source: 
+          https://github.com/ivmai/bdwgc
+          
+      Note, this option is complementary to -autofree. The Boehm garbage
+      collector is conservative, and it may make your program significantly
+      slower if it does many small allocations in a loop. This option
+      is intended *mainly* for reducing the memory usage of programs, that
+      process large amounts of text in *batch mode* on low/limited memory 
+      environments like small VPSes, and for which a few ms of garbage
+      collection pauses from time to time *do not matter much*.
+
 # Miscellaneous:
    -printfn <fn_name>
       Print the content of the generated C function named fn_name.

doc/docs.md

@@ -3698,6 +3698,9 @@ If you do need a custom flag file, that has platform dependent code, use the
 postfix `_d_customflag.v`, and then use plaftorm dependent compile time
 conditional blocks inside it, i.e. `$if linux {}` etc.
 
+- `_notd_customflag.v` => similar to _d_customflag.v, but will be used 
+*only* if you do NOT pass `-d customflag` to V.
+
 ## Compile time pseudo variables
 
 V also gives your code access to a set of pseudo string variables,

vlib/builtin/array.v

@@ -482,7 +482,7 @@ pub fn (a &array) free() {
 	// if a.is_slice {
 	// return
 	// }
-	C.free(a.data)
+	unsafe { free(a.data) }
 }
 
 [unsafe]
@@ -493,7 +493,7 @@ pub fn (mut a []string) free() {
 	for s in a {
 		unsafe { s.free() }
 	}
-	C.free(a.data)
+	unsafe { free(a.data) }
 }
 
 // str returns a string representation of the array of strings

vlib/builtin/builtin.c.v

@@ -184,7 +184,11 @@ pub fn malloc(n int) byteptr {
 		}
 		nr_mallocs++
 	} $else {
-		res = unsafe { C.malloc(n) }
+		$if gcboehm ? {
+			res = unsafe { C.GC_MALLOC(n) }
+		} $else {
+			res = unsafe { C.malloc(n) }
+		}
 		if res == 0 {
 			panic('malloc($n) failed')
 		}
@@ -214,7 +218,11 @@ pub fn v_realloc(b byteptr, n int) byteptr {
 			C.memcpy(new_ptr, b, n)
 		}
 	} $else {
-		new_ptr = unsafe { C.realloc(b, n) }
+		$if gcboehm ? {
+			new_ptr = unsafe { C.GC_REALLOC(b, n) }
+		} $else {
+			new_ptr = unsafe { C.realloc(b, n) }
+		}
 		if new_ptr == 0 {
 			panic('realloc($n) failed')
 		}
@@ -254,11 +262,16 @@ pub fn realloc_data(old_data byteptr, old_size int, new_size int) byteptr {
 			min_size := if old_size < new_size { old_size } else { new_size }
 			C.memcpy(new_ptr, old_data, min_size)
 			C.memset(old_data, 0x57, old_size)
-			C.free(old_data)
+			free(old_data)
 			return new_ptr
 		}
 	}
-	nptr := unsafe { C.realloc(old_data, new_size) }
+	mut nptr := byteptr(0)
+	$if gcboehm ? {
+		nptr = unsafe { C.GC_REALLOC(old_data, new_size) }
+	} $else {
+		nptr = unsafe { C.realloc(old_data, new_size) }
+	}
 	if nptr == 0 {
 		panic('realloc_data($old_data, $old_size, $new_size) failed')
 	}
@@ -268,7 +281,11 @@ pub fn realloc_data(old_data byteptr, old_size int, new_size int) byteptr {
 // v_calloc dynamically allocates a zeroed `n` bytes block of memory on the heap.
 // v_calloc returns a `byteptr` pointing to the memory address of the allocated space.
 pub fn v_calloc(n int) byteptr {
-	return C.calloc(1, n)
+	$if gcboehm ? {
+		return C.GC_MALLOC(n)
+	} $else {
+		return C.calloc(1, n)
+	}
 }
 
 // vcalloc dynamically allocates a zeroed `n` bytes block of memory on the heap.
@@ -280,7 +297,11 @@ pub fn vcalloc(n int) byteptr {
 	} else if n == 0 {
 		return byteptr(0)
 	}
-	return C.calloc(1, n)
+	$if gcboehm ? {
+		return C.GC_MALLOC(n)
+	} $else {
+		return C.calloc(1, n)
+	}
 }
 
 // free allows for manually freeing memory allocated at the address `ptr`.
@@ -289,6 +310,10 @@ pub fn free(ptr voidptr) {
 	$if prealloc {
 		return
 	}
+	$if gcboehm ? {
+		C.GC_FREE(ptr)
+		return
+	}
 	C.free(ptr)
 }
 
@@ -306,14 +331,6 @@ pub fn memdup(src voidptr, sz int) voidptr {
 	}
 }
 
-// v_ptr_free is used internally to manually free up memory allocated at the address `ptr`.
-fn v_ptr_free(ptr voidptr) {
-	$if prealloc {
-		return
-	}
-	C.free(ptr)
-}
-
 // is_atty returns 1 if the `fd` file descriptor is open and refers to a terminal
 pub fn is_atty(fd int) int {
 	$if windows {

vlib/builtin/builtin_d_gcboehm.v

@@ -0,0 +1,13 @@
+module builtin
+
+#define GC_THREADS 1
+
+#include <gc.h>
+
+#flag -lgc
+
+fn C.GC_MALLOC(n size_t) voidptr
+
+fn C.GC_REALLOC(ptr voidptr, n size_t) voidptr
+
+fn C.GC_FREE(ptr voidptr)

vlib/builtin/builtin_notd_gcboehm.v

@@ -0,0 +1,11 @@
+module builtin
+
+// Just define the C functions, so that V does not error because of the missing definitions.
+
+// NB: they will NOT be used, since calls to them are wrapped with `$if gcboehm ? { }`
+
+fn C.GC_MALLOC(n size_t) voidptr
+
+fn C.GC_REALLOC(ptr voidptr, n size_t) voidptr
+
+fn C.GC_FREE(ptr voidptr)

vlib/builtin/option.v

@@ -91,6 +91,6 @@ pub fn (ie &IError) free() {
 	unsafe {
 		ie.msg.free()
 		cie := &C.IError(ie)
-		C.free(cie._object)
+		free(cie._object)
 	}
 }

vlib/v/gen/c/cgen.v

@@ -422,6 +422,9 @@ pub fn (mut g Gen) init() {
 		}
 		g.comptime_defines.writeln('')
 	}
+	if g.pref.gc_mode == .boehm {
+		g.comptime_defines.writeln('#define _VGCBOEHM (1)')
+	}
 	if g.pref.is_debug || 'debug' in g.pref.compile_defines {
 		g.comptime_defines.writeln('#define _VDEBUG (1)')
 	}

vlib/v/gen/c/cheaders.v

@@ -454,9 +454,10 @@ void _vcleanup();
 	}
 #endif
 
+void v_free(voidptr ptr);
 voidptr memdup(voidptr src, int sz);
 static voidptr memfreedup(voidptr ptr, voidptr src, int sz) {
-	free(ptr);
+	v_free(ptr);
 	return memdup(src, sz);
 }
 '

vlib/v/gen/c/comptime.v

@@ -533,6 +533,9 @@ fn (mut g Gen) comp_if_to_ifdef(name string, is_comptime_optional bool) ?string
 			return '__cplusplus'
 		}
 		// other:
+		'gcboehm' {
+			return '_VGCBOEHM'
+		}
 		'debug' {
 			return '_VDEBUG'
 		}

vlib/v/gen/c/str.v

@@ -26,7 +26,11 @@ void _STR_PRINT_ARG(const char *fmt, char** refbufp, int *nbytes, int *memsize,
 		}
 		// increase buffer (somewhat exponentially)
 		*memsize += (*memsize + *memsize) / 3 + guess;
+#ifdef _VGCBOEHM     
+		*refbufp = (char*)GC_REALLOC((void*)*refbufp, *memsize);
+#else
 		*refbufp = (char*)realloc((void*)*refbufp, *memsize);
+#endif
 	}
 	va_end(args);
 }
@@ -35,7 +39,11 @@ string _STR(const char *fmt, int nfmts, ...) {
 	va_list argptr;
 	int memsize = 128;
 	int nbytes = 0;
+#ifdef _VGCBOEHM     
+	char* buf = (char*)GC_MALLOC(memsize);
+#else
 	char* buf = (char*)malloc(memsize);
+#endif
 	va_start(argptr, nfmts);
 	for (int i=0; i<nfmts; ++i) {
 		int k = strlen(fmt);
@@ -84,11 +92,18 @@ string _STR(const char *fmt, int nfmts, ...) {
 	}
 	va_end(argptr);
 	buf[nbytes] = 0;
+
+#ifdef _VGCBOEHM
+	buf = (char*)GC_REALLOC((void*)buf, nbytes+1);
+#else
 	buf = (char*)realloc((void*)buf, nbytes+1);
+#endif
+
 #ifdef DEBUG_ALLOC
 	//puts('_STR:');
 	puts(buf);
 #endif
+
 #if _VAUTOFREE
 	//g_cur_str = (byteptr)buf;
 #endif

vlib/v/pref/pref.v

@@ -17,6 +17,11 @@ pub enum BuildMode {
 	build_module
 }
 
+pub enum GarbageCollectionMode {
+	no_gc
+	boehm
+}
+
 pub enum OutputMode {
 	stdout
 	silent
@@ -153,6 +158,7 @@ pub mut:
 	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
 	// checker settings:
 	checker_match_exhaustive_cutoff_limit int = 10
 }
@@ -177,7 +183,7 @@ pub fn parse_args(known_external_commands []string, args []string) (&Preferences
 				target_arch := cmdline.option(current_args, '-arch', '')
 				i++
 				target_arch_kind := arch_from_string(target_arch) or {
-					eprintln('unknown architercture target `$target_arch`')
+					eprintln('unknown architecture target `$target_arch`')
 					exit(1)
 				}
 				res.arch = target_arch_kind
@@ -214,6 +220,23 @@ pub fn parse_args(known_external_commands []string, args []string) (&Preferences
 			'-silent' {
 				res.output_mode = .silent
 			}
+			'-gc' {
+				gc_mode := cmdline.option(current_args, '-gc', '')
+				match gc_mode {
+					'' {
+						res.gc_mode = .no_gc
+					}
+					'boehm' {
+						res.gc_mode = .boehm
+						parse_define(mut res, 'gcboehm')
+					}
+					else {
+						eprintln('unknown garbage collection mode, only `-gc boehm` is supported')
+						exit(1)
+					}
+				}
+				i++
+			}
 			'-g' {
 				res.is_debug = true
 				res.is_vlines = true

vlib/v/pref/should_compile.v

@@ -40,6 +40,19 @@ pub fn (prefs &Preferences) should_compile_filtered_files(dir string, files_ []s
 				continue
 			}
 		}
+		if file.contains('_notd_') {
+			mut allowed := true
+			for cdefine in prefs.compile_defines {
+				file_postfix := '_notd_${cdefine}.v'
+				if file.ends_with(file_postfix) {
+					allowed = false
+					break
+				}
+			}
+			if !allowed {
+				continue
+			}
+		}
 		all_v_files << os.join_path(dir, file)
 	}
 	//