I Have a LD_PRELOAD file. On what OS and conditions i should compile this preload to work on most systems (Unix/Linux). The most wanted are FreeBSD, Ubuntu, CenstOS, Solaris.
Thanks!
You need to compile it into a shared library. Here's how I typically compile mine:
libt.so: t.lo
g++ -fPIC -O3 -W -Wall -shared -Wl,-export-dynamic -o $# $^ -lc
t.lo: t.cc
g++ -c -fPIC -O3 -W -Wall $^ -o $#
Then to use it, you add the library to the LD_PRELOAD environment variable before launching that file. If you do it this way from the bash command line:
LD_PRELOAD=libt.so executable_name -and args
then, it will only set it for that command line run, and not affect any other programs you launch afterwards.
Related
For a project, I have to create a simple makefile for the source code which includes pthreads and command line arguments (if those matter to include).
The first version of the makefile that didn't work was this:
mr: mr.o
g++ -std=c++11 -pthread mr.o -o mr
mr.o: mapred.cc
g++ -std=c++11 -pthread -c mapred.cc
clean:
rm *.o mr
and I got the following error that the object file did not exist?
So then I decided to flip the two first statements around:
mr.o: mapred.cc
g++ -std=c++11 -pthread -c mapred.cc
mr: mr.o
g++ -std=c++11 -pthread mr.o -o mr
clean:
rm *.o mr
and it compiles, sort of? All I get in the terminal is:
g++ -std=c++11 -pthread -c mapred.cc
and nothing else. When I look at what files were created, all I see is a new file mapred.o created but no executable. So no errors but not fully completed. If you guys have any tips to help me out that would be very appreciated. Thank you!
If you don't specify an explicit output name with the -o option, then the compiler will name object file the same as the source file but with an .o suffix.
In your case, the command
g++ -std=c++11 -pthread -c mapred.cc
will create an object file named mapread.o.
Either use mapread.o for your target names and when linking, or use the -o option:
g++ -std=c++11 -pthread -c mapred.cc -o mr.o
As for your second problem, unless you specify an explicit target when invoking make, it will only use the first target and nothing else.
I am trying to compile a program consisting of two source files:
wildcardtrie.h, wildcardtrie.cpp
using a Makefile. However, when I run GDB to debug, I get the following error:
Reading symbols from /home/meric/Documents/Random/SectionLeading/wildcardtrie...(no debugging symbols found)...done.
I have tried a number of different compiler flags, none of which worked. The thing that perplexes me is that I have used a nearly identical Makefile in other programs and missing symbols has never been a problem. I have included the Makefile below:
CC=g++
CFLAGS = -g -ggdb g++ -O0 -Wall -Wfloat-equal -Wtype-limits -Wpointer-arith -Wlogical- op -fno-diagnostics-show-option
LDFLAGS = -g -ggdb -std=c++0x
programs = wildcardtrie
all : $(programs)
clean:
rm -f $(programs) core *.o
.PHONY: clean all
I have tried removing '-g' and '-ggdb' in the compiler and linker flags, but nothing seems to work. When I call 'make', I get the following output on the terminal:
g++ -c -o wildcardtrie.o wildcardtrie.cpp
g++ -g -ggdb -std=c++0x wildcardtrie.o -o wildcardtrie
Any help would be greatly appreciated!
g++ -c -o wildcardtrie.o wildcardtrie.cpp
This clearly shows that -g is not on your compile line (which is exactly the cause of your problem).
To get -g there, either add it to CXXFLAGS (this is the preferred solution), or just write the compile rule explicitly (instead of relying on built-in make rule):
wildcardtrie.o: wildcardtrie.cpp
$(CC) $(CFLAGS) -o wildcardtrie.o wildcardtrie.cpp
I'm building a package which provides many makefiles, each makefile has hard coded in side something like
CFLAGS = -g -O2 -Wall ...
CXXFLAGS = -g -O2 -Wall ...
I want to discard -g option but I don't want to edit all makefiles (even not automatically with sed or something similar). The configure script which comes with the package doesn't have enable/disable debug option but I can pass it CFLAGS and CXXFLAGS variables and it concatenates their values to the CFLAGS and CXXFLAGS variables respectively which include the -g option.
Is there an option which will discard -g in case it is specified? Something like
gcc -option-im-looking-for -g file.c -o file
Will build the binary file without debug symbols. I don't want to strip the binary, I want it to be created stripped.
You could negate the effect of -g by adding -g0. Saying
gcc -g -g0 foo.c -o file.o
would produce a binary identical to one obtained by saying
gcc foo.c -o foo.o
Quoting man gcc:
-glevel
...
Level 0 produces no debug information at all. Thus, -g0 negates
-g.
You don't need to edit makefiles. Just override the variables on the command line:
$ cat Makefile
CFLAGS = -g -Wall
all:
echo $(CFLAGS)
$ make
echo -g -Wall
-g -Wall
$ make CFLAGS=-Wall
echo -Wall
-Wall
When I want to compile, I need to specify -std=c++11 like this:
g++ -Wall -std=c++11 main.cpp -o main
and I wonder if there was a solution to set the -std=c++11 flag permanently so it will be possible to do:
g++ -Wall main.cpp -o main
without flags.
Create an alias: alias g++='g++ -std=c++11' should do the trick.
(However, the version of GCC that comes with OS X is so ancient that it doesn't support C++11, you'd be better off using clang and clang++.)
I know this already has an accepted but I feel like I have some advice to offer. For one you should be using a makefile for c++, this is the one I use for answering on SO.
CFLAGS=-std=c++11
CFLAGS+=-stdlib=libc++
CC=clang++
#flags for test.c
cc=clang
DEBUG=-g
#warnings
WARNINGS=-Weverything
#always have -Weverything on for SO lol
OPT= -O0 -O1 -O2 -O3 -O4
test: test.cpp
$(info set CC for compiler)
$(CC) $(CFLAGS) $< -o $# $(DEBUG)
stack: stack.cpp
$(CC) $(CFLAGS) stack.cpp -o $# $(DEBUG) $(WARNINGS)
testc: test.c
$(cc) $< -o $# $(DEBUG)
clean:
rm test
Now whenever I download someones crappy code from SO I have a makefile for c and c++ files where I can easily change the flags if I want to.
As for bash alias I would suggest you alias it like so alias clang++11='clang++ -std=c++11 this way you don't overwrite the clang++ if you don't want to use the c++11 standard. Lastly you can add the line I just showed you to your .bash_profile on a mac which is in your home or ~ folder, this will make the change permanent. Once you change it run source .bash_profile to put the changes into effect. On linux I think the file is called .bashrc. Hopefully these tips will help you out when ur c++ing, I would advise you to learn the mac command line, has differences from the linux one, it can be very useful to know some of the things it can do.
my program compiles nicely for Android, however when I try to copy it to the Android emulator, it gives the following error:
knight666#Katja-Linux /media/Data/Shared/Galaxians $ acpy Galaxians.android
Filename: 'Galaxians.android'
819 KB/s (420657 bytes in 0.501s)
link_image[1638]: 825 could not load needed library 'libstdc++.so.6' for '/system/sbin/Galaxians.android' (load_library[984]: Library 'libstdc++.so.6' not found)CANNOT LINK EXECUTABLE
acpy is a small script I wrote that does the following:
#!/bin/sh
FILEPATH=`dirname $1`
FILENAME=`basename $1 .c`
echo "Filename: '$FILENAME'"
adb push $FILEPATH/$FILENAME /system/sbin/$FILENAME
adb shell chmod 777 /system/sbin/$FILENAME
adb shell /system/sbin/$FILENAME
Here is how I build my application:
oem#androiddev /media/YoghurtGum/Tests/Galaxians $ sudo make
arm-none-linux-gnueabi-g++ -static-libgcc -g -Wall -Werror -O2 -w -I ../../YoghurtGum/src/GLES -I ../../YoghurtGum/src -c src/Alien.cpp -o intermediate/Alien.o
arm-none-linux-gnueabi-g++ -static-libgcc -g -Wall -Werror -O2 -w -I ../../YoghurtGum/src/GLES -I ../../YoghurtGum/src -c src/Bullet.cpp -o intermediate/Bullet.o
arm-none-linux-gnueabi-g++ -static-libgcc -g -Wall -Werror -O2 -w -I ../../YoghurtGum/src/GLES -I ../../YoghurtGum/src -c src/Game.cpp -o intermediate/Game.o
arm-none-linux-gnueabi-g++ -static-libgcc -g -Wall -Werror -O2 -w -I ../../YoghurtGum/src/GLES -I ../../YoghurtGum/src -c src/Player.cpp -o intermediate/Player.o
arm-none-linux-gnueabi-gcc
-Wl,--entry=main,
-dynamic-linker=/system/bin/linker,
-rpath-link=/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib,
-rpath=../../YoghurtGum/lib/Android,
-L/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib
-nostdlib
-lstdc++
intermediate/Alien.o
intermediate/Bullet.o
intermediate/Game.o
intermediate/Player.o
../../YoghurtGum/lib/Android/libstdc++.a
../../YoghurtGum/bin/YoghurtGum.a
-o bin/Galaxians.android
Line breaks are only for clarity, none exist in the actual output.
YoghurtGum is my game library that already statically and dynamically links to libstdc++.
When I remove lstdc++, the program doesn't compile because it can't find the library.
Is there a way to link to stdlibc++ statically or link the application to the correct dynamic library in the emulator?
Thanks in advance.
There is a modification of the ndk with support for exceptions, RTTI and stdlibc++.
http://www.crystax.net/android/ndk-r3.php
The other alternative involves porting just what you need, by hand... eek!