I'm trying to see if I can use stdio.h with a simple XDP code that blocks every packet.
#include <linux/bpf.h>
#include <stdio.h>
int main()
{
return XDP_DROP;
}
This code works without stdio.h but it wouldn't compile when I try to compile it using :
clang -target bpf -O2 -c xdp.c -o xdp.o
I was thinking maybe the compiler cannot find the system headers' directory so I also tried :
clang -target bpf -O2 -c xdp.c -o xdp.o -I /usr/include/
which I believe should specify where the system header files are.
I don't know what is wrong :(
Related
I 'm newbie.(And I cannot speak English better.)
I'm trying compile Nim code using gtk
{.push header:"<gtk/gtk.h>",varargs.}
proc gtk_init(argc,argv:pointer=nil)
proc gtk_window_new(typ:int):pointer
proc gtk_main_quit
proc gtk_widget_show(win:pointer)
proc gtk_main
{.pop.}
var maindow:pointer
gtk_init()
maindow=gtk_window_new(0)
maindow.gtk_widget_set_size_request(300,200)
maindow.gtk_widget_show()
gtk_main()
I'm using this command ->
nim c -r test
However,It couldn't succeed.
fatal error: gtk/gtk.h: No such file or directory
#include <gtk/gtk.h>
^~~~~~~~~~~
compilation terminated.
I already installed libgtk-3-dev ,but didn't solved the problem.
(so I don't know that syntax of the code is correct.)
What should I do for compile it?
When you use GTK from a C program, you have to pass the correct include directories with -I and the correct linked libraries with -l. Usually, these are obtained by calling pkg-config:
$ pkg-config --cflags gtk+-3.0
-pthread -I/usr/include/gtk-3.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/at-spi-2.0 -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -I/usr/include/gtk-3.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng16 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include
$ pkg-config --libs gtk+-3.0
-lgtk-3 -lgdk-3 -lpangocairo-1.0 -lpango-1.0 -latk-1.0 -lcairo-gobject -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0
Thus, to tell Nim to pass the right flags to the C compiler and linker, you can do the following:
{.passc: staticExec("pkg-config --cflags gtk+-3.0").}
{.passl: staticExec("pkg-config --libs gtk+-3.0").}
{.push header:"<gtk/gtk.h>",varargs.}
proc gtk_init(argc,argv:pointer=nil)
proc gtk_window_new(typ:int):pointer
proc gtk_main_quit
proc gtk_widget_show(win:pointer)
proc gtk_main
{.pop.}
var maindow:pointer
gtk_init()
...
Such usage of GTK wouldn't be very typical though. You may find it easeir to just use an existing wrapper such as nim-gtk3.
I'm trying to build lstrip, a Lua utility for compressing Lua source code. I'm trying to build for Lua 5.1.3 on OS X v10.10.3.
I have downloaded and extracted the Lua 5.1.3 source code and modified the Makefile for lstrip to point to this directory. However, when I run make, I get this output:
cc -I/usr/local/src/lua-5.1.3/src -I/usr/local/src/lua-5.1.3/src -O2 -Wall -Wextra -O2 -c -o lstrip.o lstrip.c
lstrip.c:33:14: warning: unused parameter 'argc' [-Wunused-parameter]
int main(int argc, char* argv[])
^
1 warning generated.
sed '/void luaX_next/i#include "proxy.c"' /usr/local/src/lua-5.1.3/src/llex.c > llex.c
sed: 1: "/void luaX_next/i#inclu ...": command i expects \ followed by text
make: *** [llex.c] Error 1
This is what the relevant Makefile command looks like:
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
I think that this is because the # in the sed command is being treated like an actual comment, but I'm not sure.
How can I fix the Makefile, or manually run the steps, to get lstrip built?
Full copy of the Makefile follows, in case it matters:
# makefile for lstrip
# change these to reflect your Lua installation (Lua 5.1!)
LUA= /usr/local/src/lua-5.1.3
LUAINC= $(LUA)/src
LUALIB= $(LUA)/src
LUASRC= $(LUA)/src
# no need to change anything below here
CFLAGS= $(INCS) $(WARN) -O2 $G
WARN= -O2 -Wall -Wextra
INCS= -I$(LUAINC) -I$(LUASRC)
LIBS= -L$(LUALIB) -llua -lm
MYNAME= lstrip
MYLIB= $(MYNAME)
T= $(MYNAME)
OBJS= $(MYNAME).o llex.o
TEST= test.lua
all: test
test: $T
$T $(TEST)
$T: $(OBJS)
$(CC) -o $# $(OBJS) $(LIBS)
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
llex.o: proxy.c
clean:
-rm -f $(OBJS) core core.* a.out $(MYNAME)
# eof
Hand-build solution:
cp /usr/local/src/lua-5.1.3/src/llex.c .
Hand-edit llex.c to add the line #include "proxy.c" before the line starting with void luaX_next (line 446 for me).
Now run make, which will succeed.
You can find the answer in the sed manual, and it is in the Makefile lines
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
Some variable expansion takes place here:
$(LUASRC) is expanded to the variable set above -> $(LUA)/src. Recurse as needed.
$# is replaced with the current target (llex.c)
So this recipe says:
In order to obtain the target llex.c (which will be processed later through other recipes), apply a stream editing command to the file $LUASRC/llex.c and write it to llex.c.
The stream editing command is: look for text "void luaX_next", before printing it, insert line "#include "proxy.c"".
Problem is, the command to do this is not "i" but "i\(newline)", which conflicts with a requirement of Makefiles that recipes must be on a single line.
I suspect that in order to fix your Makefile you need to use a different command than sed; awk can fit the bill although it's a bit more complex.
This line works in Mac OS X and in Linux:
sed '/void luaX_next/{h;s/.*/#include "proxy.c"/;p;g;}' $(LUASRC)/$# > $#
I have written lex and yacc program for calculator. In yacc program I have included math.h for arithmetic operations like sin, cos, pow etc. for compilation i use below steps
lex calculator.
yacc -d calculator.y
cc -c lex.yy.c y.tab.c
cc lex.yy.c y.tab.c -o a.out
It gives me this error:
y.tab.c:undefined reference to 'pow'
Add -lm to the 2nd cc command-line:
cc lex.yy.c y.tab.c -o a.out -lm
The pow function is defined in the library named m (which is a shorthand for math), and this library must be linked (-l) to the executable so that the function is available at runtime.
I'm working on learning C from a family member who's very adept as far as I know.
I'm using MingW on windows 7 with a fresh install of windows and having some difficulties getting things to work properly. I've made a make file and am using Deitel C for programmers with an introduction to C11, and have typed up the examples from the book in chapter three. I'm fairly certain I've managed to get that portion correct, and the makefile I'm using seems to be correct but it gives me a strange error that I don't understand.
C -o ex01 -O3 -Wall -Werrors -static -pedantic-errors -g main.o
make: C: Command not found
make: * [ex01] Error 127
this is the exact error I keep getting, I'm not sure if there's something wrong with the makefile or if it's something wrong with settings...
RM=rm
CC=gcc
LINK=$CC
CFLAGS = -O3 -Wall -Werrors -static -pedantic-errors -g
all: main.o ex01
clean:
(Tab)$(RM) -f main.o ex01.exe
main.o: main.c
(Tab)$(CC) -o main.o $(CFLAGS) -c main.c
ex01: main.o
(Tab)$(LINK) -o ex01 $(CFLAGS) main.o
this is almost exactly the makefile I'm using, asside from the (Tab) in place of actual tabs. I hope this is enough information to get some help, I suspect it's something wrong with my settings, I've had to set up paths to my library and gcc location. I'm just not sure where else to set up a path that could rectify this error.
#Keltar's comment nailed it exactly: LINK=$CC should be LINK=$(CC).
In make's syntax, $() is the proper way to deference a variable. The line LINK=$(CC) means set the variable LINK to whatever the CC variable is set to. After that instruction, their values will be the same.
I'm trying to write a Makefile which should download some sources if and only if they are missing.
Something like:
hello: hello.c
gcc -o hello hello.c
hello.c:
wget -O hello.c http://example.org/hello.c
But of course this causes hello.c to be downloaded every time make command is run. I would like hello.c to be downloaded by this Makefile only if it is missing. Is this possible with GNU make and how to do this if it is?
My guess is that wget doesn't update the timestamp on hello.c, but retains the remote timestamp. This causes make to believe that hello.c is old and attempts to download it again. Try
hello.c:
wget ...
touch $#
EDIT: The -N option to wget will prevent wget from downloading anything unless the remote file is newer (but it'll still check the timestamp of the remote file, of course.)
Since the Makefile should be working as you want, you need to check a few unlikely cases:
1) Check that you don't have any .PHONY rules mentioning the source file.
2) Check that the source target name matches the file path you are downloading.
You could also try running make -d to see why make thinks it needs to 're-build' the source file.
The Makefile you wrote downloads hello.c only if it's missing. Perhaps you are doing something else wrong? See for example:
hello: hello.c
gcc -o hello hello.c
hello.c:
echo 'int main() {}' > hello.c
And:
% make
echo 'int main() {}' > hello.c
gcc -o hello hello.c
% rm hello
% make
gcc -o hello hello.c
% rm hello*
% make
echo 'int main() {}' > hello.c
gcc -o hello hello.c
(the echo command was not executed the second time)
If the prerequisite for hello.c has changed or is empty and Make continues to download the file when it exists, then one option to prevent Make from re-downloading the file is to use a flag in the body of the target to detect if the file exists:
hello.c:
test -f $# || wget -O hello.c http://example.org/hello.c
The test command will return true if the hello.c file exists, otherwise it will return false and the wget command will run.