I was using soekris box for my embedded linux assignment where i had to compile my c file using -war and -werror . can any body help me how can i use this two minimal flag while compiling?
Just open the terminal and enter something like this:
gcc -x c -c -Wall -Werror ./path/to/our/fency/c/file.c ?
I added a few more flags:
`-x c` - tells the compiler that it's a C code.
`-c` - tells the compiler just to compile, no linking.
And ones You asked for:
`-Wall` - turns all warning reporting.
`-Werror` - tells to make all warnings into errors.
You can read some more about gcc flags by checking gcc --help or in documentation.
Add them to your Makefile as CFLAGS.
CFLAGS = -Wall -Werror
Related
I have a simple project with a simple configure.ac script:
AC_INIT(...)
AM_INIT_AUTOMAKE([-Wall -Werror foreign])
AC_PROG_CC
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES(...)
AC_OUTPUT
using GNU Autoconf version 2.69 (OpenSUSE Linux with gcc 9.2.1), but gcc is being called with no warning flags:
gcc -DHAVE_CONFIG_H -I. -I.. -g -O2 -MT aprog.o -MD -MP -MF .deps/aprog.Tpo -c -o aprog.o aprog.c
mv ...
gcc -g -O2 -o aprog aprog.o -lgmp
In particular, I found -Wformat not working. Shouldn't -Wall include -Wformat? And shouldn't all warnings appear on the make line? If I run gcc line directly with -Wformat the warning shows in compile but it doesn't when I run autoconf, configure and make.
What I'm doing wrong?
The -Wall flag in the AM_INIT_AUTOMAKE(...) invocation refers to warnings from automake and related tools like aclocal, not to compiler warnings. You will see these warnings when you are running autoreconf.
Note that while you can also add -Werror to AM_INIT_AUTOMAKE(...) to make your autoreconf run fail on warnings, many common macros (like those shipped with gettext or libtool) will still use deprecated macros which generates a warning, so -Werror means you cannot use this standard set of tools, so -Werror is not very useful in many cases.
If you want to add compiler options, there are a third party macros (e.g. AX_CHECK_COMPILE_FLAG) which test whether the compiler recognizes a given compile option and you can then add them to some variable and use that in places. That is a different stackoverflow question, though.
I am porting a project from VxWorks 5.x to 7 and the new version of the "gcc" (4.8.1) compiler is not displaying the "#warning" statements within my C code.
The following are the flags I am using and none of them appear to inhibit the warning messages:
-march=corei7 -mpopcnt -maes -mpclmul -mavx -mfsgsbase -mrdrnd -mf16c -mavx2 -mmovbe -mfma -mbmi -mbmi2 -mrdseed -madx -mprfchw -nostdlib -fno-builtin -fno-defer-pop -m64 -fno-omit-frame-pointer -mcmodel=$(CM) -mno-red-zone -fno-implicit-fp -ansi -fno-zero-initialized-in-bss -O2 -w -g -w
I even added '-Wall' and that had NO affect. If I replaced on of the '#warning's with '#error', the build fails, indicating that the code IS getting compiled.
Can anybody assist?
From the manual:
-w Inhibit all warning messages.
You have two of those in your command line.
I'm following Zed Shaw's tutorial "Learn C the Hard Way" and trying to teach myself c programming language.
On my ubuntu desktop, I encountered the linking problem he mentioned in the note of this post.
That is, when linking a static library with gcc, using a command like this:
gcc -Wall -g -DNDEBUG -lmylib ex29.c -o ex29
The linker fails to find the functions in the lib. To link correctly, I have to change the order of source file and lib to this:
gcc -Wall -g -DNDEBUG ex29.c -lmylib -o ex29
And I'm trying to use the makefile offered by Zed to automate unit test. The makefile looks like this:
TEST_SRC=$(wildcard tests/*_tests.c)
TESTS=$(patsubst %.c,%,$(TEST_SRC))
TARGET=build/libYOUR_LIBRARY.a
tests: CFLAGS += $(TARGET)
tests: $(TESTS)
sh ./tests/runtests.sh
The rest part of the makefile that isn't listed here can build the $(TARGET) lib flawlessly.
The problem is Zed append the lib to the $(CFLAGS) and use the implicit rule to compile the test files which leads to a command like this:
gcc -g -O2 -Wall -Wextra -Isrc -rdynamic -DNDEBUG tests/hashmap_tests.c build/mylib.a -o tests/list_tests
The command fails because of the link problem mentioned before as expected.
The solution I came up with was to write the compilation command explicitly like this so I can change the order:
$(TESTS): $(TARGET)
$(CC) $(CFLAGS) $^ $(TARGET) -o $#
This works fine if there is only one main source file. Unfortunately, I have several out there under the ./tests directory, and a command like this is a total disaster.
My question is, how should I change my makefile to make it work or is there any other way I can do the same work as elegant as expected?
CFLAGS holds compiler flags, like -g -O2. You should not add linker flags to it. CPPFLAGS holds preprocessor flags like -Isrc -DNDEBUG. LDFLAGS holds linker flags, which would include things like -L (capital L) if you need it to find libraries, and -rdynamic. And the LDLIBS variable holds libraries, so you should do this:
CPPFLAGS = -Isrc -DNDEBUG
CFLAGS = -g -O2 -Wall -Wextra
LDFLAGS = -rdynamic
LDLIBS = -lmylib
Now you can use the built-in rules for GNU make to build your program. You can see a list of the build-in rules by running make -p -f/dev/null.
Of course the above are just the default variables make defines and uses with its default rules. You don't have to use them, but in general it's better to follow conventions rather than flaunt them.
I need help it is bug or I don't understand how compilation options are working ?
I have sample main.c file and try to compile it as:
$ g++ -nostdlib -g -fno-rtti -fno-exceptions -ffreestanding -nostdinc -nostdinc++ -Wl,--build-id=none,-g,-nostdlib,-nostartfiles,-zmax-page-size=0x1000 main.c -o main
and as output I have this:
$ ls
main.c startfiles
I am trying to understand why g++ created file named "startfiles" not "main" ?
If you read the GNU ld official documentation you will see that there is no option named -nostartfiles. What you do pass for arguments to the linker with that is the options -n and -ostartfiles.
If I were you, I would check those other options you try to pass to the linker as well.
-nostartfiles is a compiler flag as far as I know, not a linker flag.
For the linker, it's the same as -n -o startfiles, which is why you're getting that output file name.
I am trying to run program from the Learn C Hard Way book
I need to pass the library filename 'build/liblcthw.a' as the last parameter.
For eg :
Doesnt Work on Ubuntu :
gcc -g -O2 -Wall -Wextra -Isrc -rdynamic -DNDEBUG build/liblcthw.a tests/list_tests.c -o tests/list_tests
Works on Ubuntu :
gcc -g -O2 -Wall -Wextra -Isrc -rdynamic -DNDEBUG tests/list_tests.c -o tests/list_tests build/liblcthw.a
How do I handle this in Makefile ? CFLAGS will only add it before the source filename and it doesnt work. How do I force CFALGS to add the library filename at the end of the command ?
CFLAGS are flags for the C compiler. Libraries typically go into a variable called LDLIBS. Set LDLIBS=build/liblcthw.a and see if that works.
The first invocation doesn't succeed because the order of sources and libraries in the command line is wrong. The correct order is source files, then object files, followed by static libraries followed by dynamic libraries.