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##C/C++ related##

###makefile###

if the makefile does not have default name like makefile or Makefile, it is possible to specify the filename like the following:

make -f Makefile2
#OR
make --file=Makefile2

PHONY: (avoid conflicting with exsiting files)

.PHONY: clean
clean: *.o

@ is used to turn off echoing.

wildcard useage is tha same as bash.

% is used to do 'grep-like' matching.

= i s used to define variables. Advanced variations are :=, ?=, +=.

?= if it doesn't have a value, set it.

+= append

:= expansion is done immediately, can be used in the begining of the file, followed by empty. All the following will be appended by +=.

$(VARIABLE) and ${VARIABLE} are equivalent in referring to variables.

$$ for environmental variable

test:
    @echo $$HOME

Example for checking system:

OSUPPER = $(shell uname -s 2>/dev/null | tr "[:lower:]" "[:upper:]")
OSLOWER = $(shell uname -s 2>/dev/null | tr "[:upper:]" "[:lower:]")

OS_SIZE    = $(shell uname -m | sed -e "s/x86_64/64/" -e "s/armv7l/32/" -e "s/aarch64/64/")
OS_ARCH    = $(shell uname -m)
ARCH_FLAGS =

DARWIN = $(strip $(findstring DARWIN, $(OSUPPER)))
ifneq ($(DARWIN),)
    XCODE_GE_5 = $(shell expr `xcodebuild -version | grep -i xcode | awk '{print $$2}' | cut -d'.' -f1` \>= 5)
endif

# Take command line flags that override any of these settings
ifeq ($(x86_64),1)
    OS_SIZE = 64
    OS_ARCH = x86_64
endif
ifeq ($(ARMv7),1)
    OS_SIZE    = 32
    OS_ARCH    = armv7l
    ARCH_FLAGS = -target-cpu-arch ARM
endif
ifeq ($(aarch64),1)
    OS_SIZE    = 64
    OS_ARCH    = aarch64
    ARCH_FLAGS = -target-cpu-arch ARM
endif

Automatic Vairables

target: dependency1 dependency2

  1. $@: current Target

    (@D), (@F): current Directory and File

  2. $<: dependency1

    $(<D), $(<F): dependency1 Directory and File

  3. $^: all dependencies

  4. $*: captured by %

  5. $?: dependencies that is newer than target

example:

%.o: %.cpp
    $(CXX) $(CPPFLAGS) $(LDFLAGS) -o $@ -c $< $(LIBS)

or:

    $(CXX) $(CPPFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)

search for .h file:

find /usr/ -name "*.h" |grep host

###makefile in C compiling###

CXX, CXXFLAGS is related to c++ compiler g++, CPP, CPPFLAGSis related to pre processor (not c plus plus).

CC, CFLAGS is for c compiler cc.

-I in CFLAGS is to set to include non-standard directories.

LDFLAGS if for the linker, -l is for specific library files and -L is the library search path.

###use cmake###

typical usage:

cmake .
make

###gcc###

gcc optinos:

  1. -g: extra debugging info
  2. -o: file output should be named file
  3. -c: compile without linking (output .o file)
  4. -O, -O2 turn on optimizations

disable dynamic-linked library.

-static

opposite: use dynamic library as much as possible.

-share

example:

gcc file1.c fil2.c -o myprog

this is the same as:

gcc -c file1.c
gcc -c file2.c
gcc file1.o file2.o -o myprog

-D define macro:

gcc -DDEBUG

-U undefine macro.

show search path:

gcc -v -E main.c > /dev/null
gcc -H main.c

output this:

COLLECT_GCC_OPTIONS='-v' '-E' '-mtune=generic'
 /usr/libexec/gcc/x86_64-redhat-linux/4.4.7/cc1 -E -quiet -v main.c -mtune=generic
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/4.4.7/include-fixed"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc/x86_64-redhat-linux/4.4.7/include
 /usr/include
End of search list.

###gdb###

gdb need to be compiled by gcc with -g option.

gdb options:

command line effect
r run
l list
q quit

print variable a:

p <a>

add breakpoint at line 5:

break <5>

add breakpoint at function:

break <function>

show all breakpoints:

info break

show assembly code:

disas <functionName>

###valgrind###

track errors like:

  1. uninitialized variable
  2. memory leak
  3. buffer overflow

does not detect:

  1. static memory errors
  2. if the error does not occur during runtime

###gprof###

compile with -pg and run gprof, a gmon.out file will be generated.

###ctags###

to setup:

ctags -R

ctrl+] and ctrl+t (ctrl+o) to go into a function and go back.

###miscellaneous###

awk trick statistics:

ls -l  *.cpp *.c *.h | awk '{sum+=$5} END {print sum}'

or do this:

wc -l *.cpp *.h

###C/C++ programming###

whereis stdio.h
whereis cuda.h

###miscellaneous###

to inspect object file: (to be elaborated later)

ldd
nm