使用-std = c ++ 11的Makefile

Question

I am writing a makefile for my program (that is tested and works) The problem I can tell is that some how my '-std=c++11' is not running in the function. The code pops out a unrecognized error that I dont get when I simply run 'g++ -o exe -std=c++11 *.cpp'. Here is my make file.

HEADERS = card.h sortedLinkedList.h deck.h
OBJECTS = card.o sortedLinkedList.o deck.o main.o
exe: $(OBJECTS)
   g++ -std=c++11 $^ -o $@
%.o: %.cpp $(HEADERS)
   g++ -c -std=c++11 $< -o $@
clean:
   rm -i *.o exe

The output of my makefile is

me@root:~/Documents/CS216/Lab8$ make
g++    -c -o card.o card.cpp
card.cpp: In member function ‘void Card::print()’:
card.cpp:55:28: error: ‘to_string’ was not declared in this scope
       cardN=to_string(point);
                            ^
<builtin>: recipe for target 'card.o' failed
make: *** [card.o] Error 1

note: to_string() is not defined until c++11

daniel@Reimann:~/Documents/CS216/Lab8$ ls 
card.cpp  deck.cpp  Lab8      lab8source.zip        SortedLinkedList.h
card.h    deck.h    lab8.cpp  makefile              SortedLinkedList.o
card.o    deck.o    lab8.o    SortedLinkedList.cpp

Output of xxd makefile

00000000: 4845 4144 4552 5320 3d20 6361 7264 2e68  HEADERS = card.h
00000010: 2073 6f72 7465 644c 696e 6b65 644c 6973   sortedLinkedLis
00000020: 742e 6820 6465 636b 2e68 0a4f 424a 4543  t.h deck.h.OBJEC
00000030: 5453 203d 2063 6172 642e 6f20 536f 7274  TS = card.o Sort
00000040: 6564 4c69 6e6b 6564 4c69 7374 2e6f 2064  edLinkedList.o d
00000050: 6563 6b2e 6f20 6c61 6238 2e6f 0a4c 6162  eck.o lab8.o.Lab
00000060: 383a 2024 284f 424a 4543 5453 290a 0967  8: $(OBJECTS)..g
00000070: 2b2b 202d 7374 643d 632b 2b31 3120 245e  ++ -std=c++11 $^
00000080: 202d 6f20 2440 0a25 2e6f 3a20 252e 6370   -o $@.%.o: %.cp
00000090: 7020 2428 4845 4144 4552 5329 200a 0967  p $(HEADERS) ..g
000000a0: 2b2b 202d 6320 2d73 7464 3d63 2b2b 3131  ++ -c -std=c++11
000000b0: 2024 3c20 2d6f 2024 400a 636c 6561 6e3a   $< -o $@.clean:
000000c0: 0a09 726d 202d 6920 2a2e 6f20 4c61 6238  ..rm -i *.o Lab8
000000d0: 0a                            

Answer 1

I believe the problem is in this line:

HEADERS = card.h sortedLinkedList.h deck.h
#----------------^

You have specified a dependency on sortedLinkedList.h , but that file doesn't exist. You only have SortedLinkedList.h with a capital S .

The rule

%.o: %.cpp $(HEADERS)
    g++ -c -std=c++11 $< -o $@

is considered for making card.o but rejected because one of the prerequisites (namely sortedLinkedList.h ) doesn't exist.

So make falls back to its built-in rule for making .o files from .cpp files, which is $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c .

CXX is set to g++ by default, but CPPFLAGS and CXXFLAGS are empty. This explains the extra spaces between g++ and -c in the output:

g++    -c -o card.o card.cpp

You can confirm this by running make -r , which disables all built-in rules. It should now fail to find a rule for making card.o .

To solve this, you should fix the capitalization of SortedLinkedList.h . You should also consider using the built-in rules and just set CXXFLAGS = -std=c++11 .

Answer 2

Generally you want to use the CXXFLAGS implicit variable to specify this switch. I am not sure why the current pattern rule is failing, but using CXXFLAGS will allow getting rid of it entirely