Any idea about what I might be doing wrong? The t function is indeed local to the library. This could happen due to a number or reasons. The most likely ones are: You declared the function static, or You compiled the library with -fvisibility=hidden and did not have __attribute__((visibility(“default”))) on the function, or You linked … Read more
In x86-64, 32-bit instructions implicitly zero-extend: bits 32-63 are cleared (to avoid false dependencies). So sometimes that’s why you’ll see odd-looking instructions. (Is mov %esi, %esi a no-op or not on x86-64?) However, in this case the previous mov-load is also 32-bit so the high half of %rax is already cleared. The mov %eax, %eax … Read more
__GNUC__ doesn’t mean GCC specifically. All compilers that support GNU C extensions define it, including clang and ICC. The normal way to detect specifically GCC is by excluding other “compatible” compilers #if defined(__GNUC__) && !defined(__llvm__) && !defined(__INTEL_COMPILER) #define REAL_GCC __GNUC__ // probably #endif The Clang front-end defines __clang__, but other front-ends that use the LLVM … Read more
A quick hacky fix might just to cast to long instead of int. On a lot of systems, sizeof(long) == sizeof(void *). A better idea might be to use intptr_t. int threadnumber = (intptr_t) param; and pthread_create(&(tid[i]), &attr, runner, (void *)(intptr_t)i);
These instruction prefixes have no effect on modern processors (anything newer than Pentium 4). They just cost one byte of code space, and thus, not generating them is the right thing. For details, see Agner Fog’s optimization manuals, in particular 3. Microarchitecture: http://www.agner.org/optimize/ The “Intel® 64 and IA-32 Architectures Optimization Reference Manual” no longer mentions … Read more
A look in the GCC 4.9.2 source code (gcc/opts.c) showed that -Og is the the same as -O1, but with some flags disabled that could result in a worse debugging experience: /* in function default_options_optimization: */ case OPT_Og: /* -Og selects optimization level 1. */ opts->x_optimize_size = 0; opts->x_optimize = 1; opts->x_optimize_fast = 0; opts->x_optimize_debug … Read more
From the gnu cpp manual… __GNUC__ __GNUC_MINOR__ __GNUC_PATCHLEVEL__ These macros are defined by all GNU compilers that use the C preprocessor: C, C++, Objective-C and Fortran. Their values are the major version, minor version, and patch level of the compiler, as integer constants. For example, GCC 3.2.1 will define __GNUC__ to 3, __GNUC_MINOR__ to 2, … Read more
unwind’s explanation is the literal truth (one minor directional error notwithstanding), but doesn’t explain why. %ebp is the “base pointer” for your stack frame. It’s the pointer used by the C runtime to access local variables and parameters on the stack. Here’s some typical function prologue code generated by GCC (g++ to be precise) First … Read more
Try using #undef: #define FOO “” #if …. #undef FOO #define FOO “Foo, good sir” #endif
From: http://gcc.gnu.org/onlinedocs/cpp/Environment-Variables.html CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH OBJC_INCLUDE_PATH Each variable’s value is a list of directories separated by a special character, much like PATH, in which to look for header files. The special character, PATH_SEPARATOR, is target-dependent and determined at GCC build time. For Microsoft Windows-based targets it is a semicolon, and for almost all other targets … Read more