add --debug-rt CLI arg to the compiler + bonus edits

The flag makes compiler_rt and libfuzzer be in debug mode.

Also:
* fuzzer: override debug logs and disable debug logs for frequently
  called functions
* std.Build.Fuzz: fix bug of rerunning the old unit test binary
* report errors from rebuilding the unit tests better
* link.Elf: additionally add tsan lib and fuzzer lib to the hash

3 files changed, 10 insertions, 1 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index bc5a2bb456..8808e72e04 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -2180,7 +2180,9 @@ pub fn update(comp: *Compilation, main_progress_node: std.Progress.Node) !void {
                 comp.bin_file = try link.File.createEmpty(arena, comp, emit, whole.lf_open_opts);
             }
         },
-        .incremental => {},
+        .incremental => {
+            log.debug("Compilation.update for {s}, CacheMode.incremental", .{comp.root_name});
+        },
     }
 
     // From this point we add a preliminary set of file system inputs that
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index ecb38974ca..7c1d695bd9 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -2286,6 +2286,8 @@ fn linkWithLLD(self: *Elf, arena: Allocator, tid: Zcu.PerThread.Id, prog_node: s
         }
         try man.addOptionalFile(module_obj_path);
         try man.addOptionalFile(compiler_rt_path);
+        try man.addOptionalFile(if (comp.tsan_lib) |l| l.full_object_path else null);
+        try man.addOptionalFile(if (comp.fuzzer_lib) |l| l.full_object_path else null);
 
         // We can skip hashing libc and libc++ components that we are in charge of building from Zig
         // installation sources because they are always a product of the compiler version + target information.
diff --git a/src/main.zig b/src/main.zig
index 9940312bcd..ddd2e79f44 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -655,6 +655,7 @@ const usage_build_generic =
     \\  --debug-log [scope]          Enable printing debug/info log messages for scope
     \\  --debug-compile-errors       Crash with helpful diagnostics at the first compile error
     \\  --debug-link-snapshot        Enable dumping of the linker's state in JSON format
+    \\  --debug-rt                   Debug compiler runtime libraries
     \\
 ;
 
@@ -912,6 +913,7 @@ fn buildOutputType(
     var minor_subsystem_version: ?u16 = null;
     var mingw_unicode_entry_point: bool = false;
     var enable_link_snapshots: bool = false;
+    var debug_compiler_runtime_libs = false;
     var opt_incremental: ?bool = null;
     var install_name: ?[]const u8 = null;
     var hash_style: link.File.Elf.HashStyle = .both;
@@ -1367,6 +1369,8 @@ fn buildOutputType(
                         } else {
                             enable_link_snapshots = true;
                         }
+                    } else if (mem.eql(u8, arg, "--debug-rt")) {
+                        debug_compiler_runtime_libs = true;
                     } else if (mem.eql(u8, arg, "-fincremental")) {
                         dev.check(.incremental);
                         opt_incremental = true;
@@ -3408,6 +3412,7 @@ fn buildOutputType(
         // noise when --search-prefix and --mod are combined.
         .global_cc_argv = try cc_argv.toOwnedSlice(arena),
         .file_system_inputs = &file_system_inputs,
+        .debug_compiler_runtime_libs = debug_compiler_runtime_libs,
     }) catch |err| switch (err) {
         error.LibCUnavailable => {
             const triple_name = try target.zigTriple(arena);