Makefile template for shared library https://www.topbug.net/blog/2019/10/28/makefile-template-for-a-shared-library-in-c-with-explanations/

Makefile

# Makefile template for a shared library in C
# https://www.topbug.net/blog/2019/10/28/makefile-template-for-a-shared-library-in-c-with-explanations/

CC = gcc  # C compiler
CFLAGS = -fPIC -Wall -Wextra -O2 -g  # C flags
LDFLAGS = -shared   # linking flags
RM = rm -f   # rm command
TARGET_LIB = libtarget.so  # target lib

SRCS = main.c src1.c src2.c  # source files
OBJS = $(SRCS:.c=.o)

.PHONY: all
all: ${TARGET_LIB}

$(TARGET_LIB): $(OBJS)
	$(CC) ${LDFLAGS} -o $@ $^

$(SRCS:.c=.d):%.d:%.c
	$(CC) $(CFLAGS) -MM $< >$@

include $(SRCS:.c=.d)

.PHONY: clean
clean:
	-${RM} ${TARGET_LIB} ${OBJS} $(SRCS:.c=.d)

does -O2 and -g can co exist?

@devnaga

does -O2 and -g can co exist?

From man gcc:

Unlike most other C compilers, GCC allows you to use -g' with-O'. The shortcuts taken by optimized code may occasionally produce surprising results: some variables you declared may not exist at all; flow of control may briefly move where you did not expect it; some statements may not be executed because they compute constant results or their values were already at hand; some statements may execute in different places because they were moved out of loops.

Nevertheless it proves possible to debug optimized output. This makes it reasonable to use the optimizer for programs that might have bugs.

tl;dr - yes it can.

Can you please explain its working. I mean I can see that you have generated .o files and linked em together to make the .so. I want to know like step by step execution of this makefile. (I'm new to makefiles and bash, so you might want to elaborate $^, $< etc).

There are tons information on google about Makefile. Please google by yourself. @saqibahmed515

could you tell me how can i build static library with your Makefile? and how can i specify a special directory for .d and .o files.

Better using -MMD -MP for dependencies auto-generation.

much appreciated! needed this in a pinch.

What about header file ?

@nainesh1311 You don't need to add them to the Makefile, because we should only send source files directly to the compiler and the compiler will find header files automatically.

Fix
$(SRCS:.c=.d):%.d:%.c
to
$(SRCS:.c=.o):%.o:%.c

And...
Why do you use the -MM option if you don’t have an entry point in `$(SRCS:.c=.d)? Where you using .d file?
https://renenyffenegger.ch/notes/development/languages/C-C-plus-plus/GCC/options/MM

$(CC) $(CFLAGS) -MM $< >$@ create some .d files

@dr-begemot $(SRCS:.c=.d):%.d:%.c is correct. The *.d files are used in the include line. $(SRCS:.c=.o):%.o:%.c is not needed because they are subsumed by the content of *.d files. In your link, there is an example that states main.d contains:

main.o: main.c hello-world.h print-line.h

which is exactly what your "correction" tries to add (with header files also taken care of).

@xuhdev
okay, then where entry point to
$(SRCS:.c=.d):%.d:%.c
?

You wrote: $(TARGET_LIB): $(OBJS)
where OBJS is $(SRCS:.c=.o), .c=.o, not .c=.d

I really want to understand)

$(SRCS:.c=.d):%.d:%.c is used to generate *.d files.

$(SRCS:.c=.o) are expressed in the generated *.d files. (Try to use this template in a minimum project and inspect the generated *.d files yourself.) I can write a post explaining this template, but I will not be able to do it until weekend.

How to force your way accept include path -I?

@dr-begemot I've written a blog post explaining this file: https://www.topbug.net/blog/2019/10/28/makefile-template-for-a-shared-library-in-c-with-explanations/

HTH

can any one tell me how to add shared library in my main project make file

can any one tell me how to add shared library in my main project make file

-l

for example:
gcc -w -Wall -g $(SRCS) -o test.exe $(FLAGS) -lsqlite3 -lcrypto -lconfig -lprotobuf-c -lcurl $(INCLUDE)

thanks for response

but one think i am not understanding actually i install embedded eclipse for windows when i create shared library output fill generated lib.so file as for my knowladge lib.so file generate base on linux system . why its happen like that

if i successfully generated library then where i add the this line

gcc -w -Wall -g $(SRCS) -o test.exe $(FLAGS) -lsqlite3 -lcrypto -lconfig -lprotobuf-c -lcurl $(INCLUDE)

in make
please consider the my attachment of make file

##########################################################################################################################
# File automatically-generated by tool: [projectgenerator] version: [2.27.0] date: [Sat Apr 28 17:58:48 IST 2018]
##########################################################################################################################

# ------------------------------------------------
# Generic Makefile (based on gcc)
#
# ChangeLog :
#	2017-02-10 - Several enhancements + project update mode
#   2015-07-22 - first version
# ------------------------------------------------

######################################
# target
######################################
TARGET = InfaLoraNodeRev1


######################################
# building variables
######################################
# debug build?
DEBUG = 1
# optimization
OPT = -Og


#######################################
# paths
#######################################
# source path
SOURCES_DIR =  \
Drivers/CMSIS \
Drivers/STM32L1xx_HAL_Driver \
Drivers \
InfaLibrary \
Application/User \
Application \

# firmware library path
PERIFLIB_PATH = 

# Build path
BUILD_DIR = build

######################################
# source
######################################
# C sources
C_SOURCES =  \


# ASM sources
ASM_SOURCES =  \
startup_stm32l152xe.s


######################################
# firmware library
######################################
PERIFLIB_SOURCES = 


#######################################
# binaries
#######################################
#BINPATH = usr/bin
#PREFIX = arm-none-eabi-
#CC = $(BINPATH)/$(PREFIX)gcc
#AS = $(BINPATH)/$(PREFIX)gcc -x assembler-with-cpp
#CP = $(BINPATH)/$(PREFIX)objcopy
#AR = $(BINPATH)/$(PREFIX)ar
#SZ = $(BINPATH)/$(PREFIX)size
#HEX = $(CP) -O ihex
#BIN = $(CP) -O binary -S

#BINPATH = E:\Rakesh.KS\ECLIPSE\GNU Tools ARM Embedded\7 2017-q4-major\bin
PREFIX = arm-none-eabi-
CC = $(PREFIX)gcc
AS = $(PREFIX)gcc -x assembler-with-cpp
CP = $(PREFIX)objcopy
AR = $(PREFIX)ar
SZ = $(PREFIX)size
HEX = $(CP) -O ihex
BIN = $(CP) -O binary -S
 
#######################################
# CFLAGS
#######################################
# cpu
CPU = -mcpu=cortex-m3

# fpu
# NONE for Cortex-M0/M0+/M3

# float-abi


# mcu
MCU = $(CPU) -mthumb $(FPU) $(FLOAT-ABI)

# macros for gcc
# AS defines
AS_DEFS = 

# C defines
C_DEFS =  \


# AS includes
AS_INCLUDES = 

# C includes
C_INCLUDES =  \
-IInc \

# compile gcc flags
ASFLAGS = $(MCU) $(AS_DEFS) $(AS_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections -mdivide-enabled

CFLAGS = $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections

ifeq ($(DEBUG), 1)
CFLAGS += -g -gdwarf-2
endif


# Generate dependency information
CFLAGS += -MMD -MP -MF"$(@:%.o=%.d)" -MT"$(@:%.o=%.d)"


#######################################
# LDFLAGS
#######################################
# link script
LDSCRIPT = STM32L152RETx_FLASH.ld

# libraries
LIBS = -lc -lm -lnosys 
LIBDIR = 
LDFLAGS = $(MCU) -specs=nano.specs -u _printf_float -T$(LDSCRIPT) $(LIBDIR) $(LIBS) -Wl,-Map=$(BUILD_DIR)/$(TARGET).map,--cref -Wl,--gc-sections

# default action: build all
all: $(BUILD_DIR)/$(TARGET).elf $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin


#######################################
# build the application
#######################################
# list of objects
OBJECTS = $(addprefix $(BUILD_DIR)/,$(notdir $(C_SOURCES:.c=.o)))
vpath %.c $(sort $(dir $(C_SOURCES)))
# list of ASM program objects
OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASM_SOURCES:.s=.o)))
vpath %.s $(sort $(dir $(ASM_SOURCES)))

$(BUILD_DIR)/%.o: %.c Makefile | $(BUILD_DIR) 
	$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $@

$(BUILD_DIR)/%.o: %.s Makefile | $(BUILD_DIR)
	$(AS) -c $(CFLAGS) $< -o $@

$(BUILD_DIR)/$(TARGET).elf: $(OBJECTS) Makefile
	$(CC) $(OBJECTS) $(LDFLAGS) -o $@
	$(SZ) $@

$(BUILD_DIR)/%.hex: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
	$(HEX) $< $@
	
$(BUILD_DIR)/%.bin: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
	$(BIN) $< $@	
	
$(BUILD_DIR):
	mkdir $@		

#######################################
# clean up
#######################################
clean:
	-rm -fR .dep $(BUILD_DIR)
  
#######################################
# dependencies
#######################################
-include $(shell mkdir .dep 2>/dev/null) $(wildcard .dep/*)

# *** EOF ***