I’m building a simple C++ program and I want to temporarily substitute a system supplied shared library with a more recent version of it, for development and testing. I tried setting the LD_LIBRARY_PATH variable but the linker (ld) failed with: /usr/bin/ld: cannot find -lyaml-cpp I expected that to work because according to the ld man … Read more

What does gcc’s ffast-math actually do?

I understand gcc’s –ffast-math flag can greatly increase speed for float ops, and goes outside of IEEE standards, but I can’t seem to find information on what is really happening when it’s on. Can anyone please explain some of the details and maybe give a clear example of how something would change if the flag … Read more

“/usr/bin/ld: cannot find -lz”

I am trying to compile Android source code under Ubuntu 10.04. I get an error saying, /usr/bin/ld: cannot find -lz Can you please tell me how can I fix it? What does cannot find -lz mean? Here’s the full error message: external/qemu/Makefile.android:1101: warning: overriding commands for target `external/qemu/android/avd/hw-config-defs.h’ external/qemu/Makefile.android:933: warning: ignoring old commands for target … Read more

Is errno thread-safe?

In errno.h, this variable is declared as extern int errno; so my question is, is it safe to check errno value after some calls or use perror() in multi-threaded code. Is this a thread safe variable? If not, then whats the alternative ? I am using linux with gcc on x86 architecture. 8 Answers 8