From cb69bb9caaf55b499fd573482f5039d52859872d Mon Sep 17 00:00:00 2001
From: Daniele Lacamera <root@danielinux.net>
Date: Thu, 19 Mar 2026 23:41:49 +0100
Subject: [PATCH] Fix embedded images built with the clang compiler

---
 arch.mk           |  5 ++++-
 test-app/Makefile | 14 +++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch.mk b/arch.mk
index a9de6d9e0f..18d82ebf72 100644
--- a/arch.mk
+++ b/arch.mk
@@ -1282,7 +1282,9 @@ ifeq ($(USE_CLANG),1)
   CLANG_NEWLIB_INCLUDE?=$(abspath $(dir $(CLANG_LIBC_A))/../include)
 
   CC=$(CLANG_DRIVER)
-  LD=$(CLANG_DRIVER)
+  # Keep clang for compilation, but use the GNU linker driver so linker-script
+  # LMAs for RAM sections are preserved and objcopy does not emit sparse images.
+  LD=$(CLANG_GCC_NAME)
   AS=$(CLANG_DRIVER)
   AR=$(CROSS_COMPILE)ar
   OBJCOPY?=$(CROSS_COMPILE)objcopy
@@ -1290,6 +1292,7 @@ ifeq ($(USE_CLANG),1)
 
   CFLAGS+=-isystem $(CLANG_NEWLIB_INCLUDE)
   CFLAGS+=-DWOLFSSL_NO_ATOMIC -DWOLFSSL_NO_ATOMICS
+  CFLAGS+=-Wno-unknown-attributes -Wno-error=unknown-attributes
   LDFLAGS+=-nostdlib
 endif
 
diff --git a/test-app/Makefile b/test-app/Makefile
index 1d0b1e5ad5..2d8bdbdd91 100644
--- a/test-app/Makefile
+++ b/test-app/Makefile
@@ -102,6 +102,14 @@ LDFLAGS+=-T $(LSCRIPT) -Wl,-gc-sections -Wl,-Map=image.map -nostartfiles
 
 # Setup default objcopy flags
 OBJCOPY_FLAGS+=--gap-fill $(FILL_BYTE)
+OBJCOPY_IMAGE_FLAGS:=
+
+ifeq ($(USE_CLANG),1)
+  # Clang-built ARM ELFs can keep RAM sections as loadable segments, and raw
+  # objcopy output then expands the flash-to-RAM gap into a huge sparse image.
+  # The app image only needs the flash-backed output sections.
+  OBJCOPY_IMAGE_FLAGS+=-j .text -j .edidx
+endif
 
 ifeq ($(DEBUG_UART),1)
     CFLAGS+=-DDEBUG_UART
@@ -899,15 +907,15 @@ delta-extra-data:LDFLAGS=-Wl,-Map=image.map
 
 image.bin: image.elf
 	@echo "\t[BIN] $@"
-	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) -O binary $^ $@
+	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) $(OBJCOPY_IMAGE_FLAGS) -O binary $^ $@
 
 image.hex: image.elf
 	@echo "\t[HEX] $@"
-	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) -O ihex $^ $@
+	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) $(OBJCOPY_IMAGE_FLAGS) -O ihex $^ $@
 
 image.srec: image.elf
 	@echo "\t[SREC] $@"
-	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) -O srec $^ $@
+	$(Q)$(OBJCOPY) $(OBJCOPY_FLAGS) $(OBJCOPY_IMAGE_FLAGS) -O srec $^ $@
 
 APP_OBJS := $(patsubst $(WOLFBOOT_LIB_WOLFSSL)/%, \
     $(WOLFSSL_LOCAL_OBJDIR)/%, $(APP_OBJS))