Merge pull request #23986 from mlugg/incremental-stuff

incremental: bugfix (and a debugging feature that helped me do that bugfix)

Author: mlugg

lib/compiler/build_runner.zig

@@ -236,6 +236,8 @@ pub fn main() !void {
                 graph.debug_compiler_runtime_libs = true;
             } else if (mem.eql(u8, arg, "--debug-compile-errors")) {
                 builder.debug_compile_errors = true;
+            } else if (mem.eql(u8, arg, "--debug-incremental")) {
+                builder.debug_incremental = true;
             } else if (mem.eql(u8, arg, "--system")) {
                 // The usage text shows another argument after this parameter
                 // but it is handled by the parent process. The build runner

lib/std/Build.zig

@@ -59,6 +59,7 @@ pkg_config_pkg_list: ?(PkgConfigError![]const PkgConfigPkg) = null,
 args: ?[]const []const u8 = null,
 debug_log_scopes: []const []const u8 = &.{},
 debug_compile_errors: bool = false,
+debug_incremental: bool = false,
 debug_pkg_config: bool = false,
 /// Number of stack frames captured when a `StackTrace` is recorded for debug purposes,
 /// in particular at `Step` creation.
@@ -385,6 +386,7 @@ fn createChildOnly(
         .cache_root = parent.cache_root,
         .debug_log_scopes = parent.debug_log_scopes,
         .debug_compile_errors = parent.debug_compile_errors,
+        .debug_incremental = parent.debug_incremental,
         .debug_pkg_config = parent.debug_pkg_config,
         .enable_darling = parent.enable_darling,
         .enable_qemu = parent.enable_qemu,

lib/std/Build/Step/Compile.zig

@@ -1447,6 +1447,10 @@ fn getZigArgs(compile: *Compile, fuzz: bool) ![][]const u8 {
         try zig_args.append("--debug-compile-errors");
     }
 
+    if (b.debug_incremental) {
+        try zig_args.append("--debug-incremental");
+    }
+
     if (b.verbose_cimport) try zig_args.append("--verbose-cimport");
     if (b.verbose_air) try zig_args.append("--verbose-air");
     if (b.verbose_llvm_ir) |path| try zig_args.append(b.fmt("--verbose-llvm-ir={s}", .{path}));

src/Compilation.zig

@@ -190,6 +190,8 @@ time_report: bool,
 stack_report: bool,
 debug_compiler_runtime_libs: bool,
 debug_compile_errors: bool,
+/// Do not check this field directly. Instead, use the `debugIncremental` wrapper function.
+debug_incremental: bool,
 incremental: bool,
 alloc_failure_occurred: bool = false,
 last_update_was_cache_hit: bool = false,
@@ -768,6 +770,14 @@ pub const Directories = struct {
     }
 };
 
+/// This small wrapper function just checks whether debug extensions are enabled before checking
+/// `comp.debug_incremental`. It is inline so that comptime-known `false` propagates to the caller,
+/// preventing debugging features from making it into release builds of the compiler.
+pub inline fn debugIncremental(comp: *const Compilation) bool {
+    if (!build_options.enable_debug_extensions) return false;
+    return comp.debug_incremental;
+}
+
 pub const default_stack_protector_buffer_size = target_util.default_stack_protector_buffer_size;
 pub const SemaError = Zcu.SemaError;
 
@@ -1598,6 +1608,7 @@ pub const CreateOptions = struct {
     verbose_llvm_cpu_features: bool = false,
     debug_compiler_runtime_libs: bool = false,
     debug_compile_errors: bool = false,
+    debug_incremental: bool = false,
     incremental: bool = false,
     /// Normally when you create a `Compilation`, Zig will automatically build
     /// and link in required dependencies, such as compiler-rt and libc. When
@@ -1968,6 +1979,7 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
             .test_name_prefix = options.test_name_prefix,
             .debug_compiler_runtime_libs = options.debug_compiler_runtime_libs,
             .debug_compile_errors = options.debug_compile_errors,
+            .debug_incremental = options.debug_incremental,
             .incremental = options.incremental,
             .root_name = root_name,
             .sysroot = sysroot,