[Experimental] Reduce the size of Windows builds by cleaning the MinGW debug info (#585)

* Reduce the size of Windows builds by cleaning the debug info

* Update IS_DEV_OR_DEBUG in Makefile

Makefile

@@ -869,6 +869,7 @@ ifeq ($(WINDOWS_BUILD),1)
   ifeq ($(CROSS),)
     LDFLAGS += -no-pie
   endif
+  LDFLAGS += -T windows.ld
 else ifeq ($(TARGET_RPI),1)
   LDFLAGS := $(OPT_FLAGS) -lm $(BACKEND_LDFLAGS) -no-pie
 else ifeq ($(OSX_BUILD),1)
@@ -986,7 +987,7 @@ else
   endif
 endif
 
-IS_DEV_OR_DEBUG := $(or $(filter 1,$(DEVELOPMENT)),$(filter 1,$(DEBUG)))
+IS_DEV_OR_DEBUG := $(or $(filter 1,$(DEVELOPMENT)),$(filter 1,$(DEBUG)),0)
 ifeq ($(IS_DEV_OR_DEBUG),0)
   CFLAGS += -fno-ident -fno-common -fno-asynchronous-unwind-tables -ffile-prefix-map=$(PWD)=. -D__DATE__="\"\"" -D__TIME__="\"\"" -Wno-builtin-macro-redefined
   LDFLAGS += -Wl,--build-id=none -Wl,--no-randomize-sections
@@ -1139,8 +1140,15 @@ endef
 all: $(EXE)
 
 ifeq ($(WINDOWS_BUILD),1)
+MAPFILE = $(BUILD_DIR)/coop.map
 exemap: $(EXE)
-	$(V)$(OBJDUMP) -t $(EXE) > $(BUILD_DIR)/coop.map
+	@$(PRINT) "$(GREEN)Creating map file: $(BLUE)$(MAPFILE) $(NO_COL)\n"
+	$(V)$(OBJDUMP) -t $(EXE) > $(MAPFILE)
+	@cp $(EXE) $(EXE).bak && cp $(MAPFILE) $(MAPFILE).bak
+	$(V)$(PYTHON) $(TOOLS_DIR)/clean_mapfile.py $(EXE) $(MAPFILE)
+ifeq ($(IS_DEV_OR_DEBUG),0)
+	$(V)$(OBJCOPY) -p --strip-unneeded $(EXE)
+endif
 all: exemap
 endif
 

tools/clean_mapfile.py

@@ -0,0 +1,121 @@
+#!/usr/bin/env python3
+# "tools/clean_mapfile.py"
+
+import sys
+import os
+import re
+import json
+
+def extract_int(b: bytes, offset: int, size: int) -> int:
+    return int.from_bytes(b[offset:(offset+size)], 'little')
+
+def parse_exe_sections(exe_path: str) -> list[dict]:
+    print(f'* Parsing sections from EXE: "{exe_path}"')
+
+    with open(exe_path, 'rb') as f:
+        b: bytes = f.read(4096)
+
+    if b[0:(0+2)] != b'MZ':
+        raise ValueError(f'"{exe_path}": no MZ header')
+
+    pe_offset = extract_int(b, 0x3C, 4)
+    if (pe_offset < 0x40) or (pe_offset > 4096) or (pe_offset & 7):
+        raise ValueError(f'"{exe_path}": bad LfaNew address')
+    if b[pe_offset:(pe_offset+4)] != b'PE\0\0':
+        raise ValueError(f'"{exe_path}": not a valid PE file')
+
+    x = extract_int(b, pe_offset + 4, 2)
+    if x != 0x8664:
+        raise ValueError(f'"{exe_path}": not a x86_64 executable')
+
+    num_sections = extract_int(b, pe_offset + 6, 2)
+    if (num_sections <= 0) or (num_sections > 64):
+        raise ValueError(f'"{exe_path}: bad NumberOfSections')
+
+    x = extract_int(b, pe_offset + 20, 2)
+    if (x <= 0) or (x > 256):
+        raise ValueError(f'"{exe_path}: bad SizeOfOptionalHeader.')
+
+    if extract_int(b, pe_offset + 24, 2) != 0x020B:
+        raise ValueError(f'"{exe_path}": invalid PE32+ signature')
+
+    sections = []
+    section_table = pe_offset + 24 + x
+    for i in range(num_sections):
+        x = section_table + i * 40
+        # virtual_size = extract_int(b, x + 8, 4)
+        virtual_addr = extract_int(b, x + 12, 4)
+        # size_of_raw_data = extract_int(b, x + 16, 4)
+        # ptr_to_raw_data = extract_int(b, x + 20, 4)
+        flags = extract_int(b, x + 36, 4)
+
+        discardable = bool(0x02000000 & flags)
+        sections.append({ 'virtual_addr': virtual_addr, 'discardable': discardable })
+
+    return sections
+
+def parse_map_file(map_path: str, module_name: str, sections: list[dict]) -> dict:
+    print(f'* Parsing and cleaning the MAP file: "{map_path}"')
+
+    with open(map_path, 'rt', encoding='ascii') as f:
+        map_content = f.read()
+
+    pattern = re.compile(r'^\[ *\d+\]\(sec +(\d+)\)\(fl 0x00\)\(ty +(\d+)\)\(scl +(\d+)\) \(nx 0\) 0x([0-9a-f]+) (.+)$', re.MULTILINE)
+    matches = pattern.findall(map_content)
+
+    symbols = []
+    with open(map_path, 'wt', encoding='ascii', newline='\n') as f:
+        for m in matches:
+            section_id = int(m[0])
+            symbol_type = int(m[1])
+            storage_class = int(m[2])
+            relative_addr = int(m[3], 16)
+            symbol_name = m[4]
+
+            # Target section is not discardable
+            if sections[section_id - 1]['discardable']: continue
+
+            # Debug symbol, accepted type
+            # - IMAGE_SYM_DTYPE_NULL     ("0")  | scalar
+            # - IMAGE_SYM_DTYPE_FUNCTION ("20") | subroutine
+            if symbol_type not in (0, 20): continue
+
+            # Debug symbol, accepted class
+            # - C_EXT  = 2 | external, global
+            # - C_STAT = 3 | static
+            if storage_class not in (2, 3): continue
+
+            # Debug symbol, accepted name
+            if symbol_name.startswith('.') and not symbol_name.startswith('.refptr.'): continue
+
+            # Calculate Relative Virtual Address
+            section_start = sections[section_id - 1]['virtual_addr']
+            rva = hex(section_start + relative_addr)
+
+            # Save back only the function labels, loaded on the crash screen
+            if (section_id == 1) and (symbol_type == 20):
+                f.write(f'(sec{section_id})(fl0x00)(ty{symbol_type})(scl{storage_class})(nx 0)0x{relative_addr:016x} {symbol_name}\n')
+
+            symbols.append({ 'module': module_name, 'address': rva, 'text': symbol_name })
+
+    return { 'labels': symbols }
+
+def main():
+    if len(sys.argv) != 3:
+        print(f'Usage: "{sys.argv[0]}" <exe_path> <map_path>"')
+        sys.exit(1)
+
+    exe_path = sys.argv[1]
+    map_path = sys.argv[2]
+
+    module_name = os.path.basename(exe_path)
+    sections = parse_exe_sections(exe_path)
+    symbols = parse_map_file(map_path, module_name, sections)
+
+    output_path = exe_path + '.dd64'
+    print(f'* Saving symbol database for x64dbg to "{output_path}"')
+    with open(output_path, 'wt', newline='\n') as f:
+        json.dump(symbols, f, indent=0, separators=(',', ':'))
+
+if __name__ == "__main__":
+    main()

windows.ld

@@ -0,0 +1,10 @@
+/**
+ * Removes the spam of ".ident" strings (around 50 KB), such as:
+ * "GCC: (Rev3, Built by MSYS2 project) 14.1.0",
+ * found in every compiled object file (and some static libraries).
+ */
+SECTIONS
+{
+  /DISCARD/ : { *(.rdata$zzz) }
+}
+INSERT BEFORE .rdata;