Hi. I'm writing a ray tracer. Recently, I added threading to the program to exploit the additional cores on my i5 Quad Core. In a weird turn of events the debug version of the application is now running slower, but the optimized build is running faster than before I added threading. I'm passing the "-g -pg" flags to gcc for the debug...
Will a compiler optimize tihs: bool someCondition = someVeryTimeConsumingTask(/* ... */); for (int i=0; i<HUGE_INNER_LOOP; ++i) { if (someCondition) doCondition(i); else bacon(i); } into: bool someCondition = someVeryTimeConsumingTask(/* ... */); if (someCondition) for (int i=0; i<HUGE_INNER_LOOP; ++i) ...
When I compile my code,I write gcc -g -Wall dene2 dene2.c in the console. Then gcc emits some text on the screen. I don't understand what this output means (I couldn't think of a meaningful title for that reason, sorry). I have tried Google searching but haven't had any luck. I'm not asking for a detailed examination of all of the outp...
We are required to compile C source codes using gcc in this manner: gcc -ansi -pedantic -Wall program.c I'm wondering how can I 'automate' this so when I enter: gcc program.c It will automatically compile with the 3 switches. Is this possible? ...
Hi there, Im trying to reverse the order of the following linked list, I've done so, But the reversed list does not seem to print out. Where have I gone wrong? //reverse the linked list #include <iostream> using namespace std; struct node{ int number; node *next; }; node *A; void addNode(nod...
I'm reading the gcc manual at the moment, especially the part about warning/error flags. After reading the part about the -Wextra flag, I wonder if it is useful at all. It seems that it complains about things which seem to be rather subjective or a matter of taste. I'm not that experienced with gcc, I only use it from time to time for so...
I have just changed a compiler option from 4.0 to 4.2. Now I get an error: jump to case label crosses initialization of 'const char* selectorName' It works fine in 4.0 Any ideas? ...
A requirement for a program I am writing is that it must be able to trust a configuration file. To accomplish this, I am using several kinds of hashing algorithms to generate a hash of the file at compile time, this produces a header with the hashes as constants. Dependencies for this are pretty straight forward, my program depends on c...
Hi All, My questions are divided into three parts Question 1 Consider the below code, #include <iostream> using namespace std; int main( int argc, char *argv[]) { const int v = 50; int i = 0X7FFFFFFF; cout<<(i + v)<<endl; if ( i + v < i ) { cout<<"Number is negative"<<endl; } else { ...
I have linked a library with my program. It works fine. The only problem is that there visibility errors/warnings (thousands of them). They are all of the form: newlib::method() has different visibility (default) in newlib.a and (hidden) in AppDelegate.o It is always with AppDelegate.o. I have tried to set the visibility for both the...
Hi, I am a teaching assistant of a introductory programming course, and some students made this type of error: char name[20]; scanf("%s",&name); which is not surprising as they are learning... What is surprising is that, besides gcc warning, the code works (at least this part). I have been trying to understand and I wrote the followin...
Pasted below is unoptimized GCC assembly output for "int main(){}". I'm relatively good with x86 assembly, but some of this is unfamiliar. Could someone please do a line-by-line walk-through of what's going on here? Thanks! .text .globl _main _main: LFB2: pushq %rbp LCFI0: movq %rsp, %rbp LCFI1: leave ret LFE...
GCC likes to tell me that I'm missing a specifier-qualifier-list in its error messages. I know that this means I didn't put in a correct type of something. But what exactly is a specifier-qualifier-list? Edit: Example C code that causes this: #include <stdio.h> int main(int argc, char **argv) { struct { undefined_type *foo; } b...
Hi, I have a program which writes its output using ofstream. Everything works perfectly fine on Windows when compiled with Visual Studio, but it only writes empty file on Linux when compiled with GCC. ofstream out(path_out_cstr, ofstream::out); if(out.bad()){ cout << "Could not write the file" << flush; } else{ cout << "writing"; ou...
I am trying to activate #pragma pack(push, 8) on ubuntu 10.4 (8.10 would also be nice), which uses gcc 4.4.3, but I can't get it to work. Is there something more that need to be done? There is not even a warning if I compile with -Wunknown-pragmas so gcc seems at least to acknowledge it as a known pragma. It would be nice to use the pa...
I've been thinking of how to implement a lock-free singly linked list. And to be honest, I don't see many bullet proof ways to do it. Even the more robust ways out there that use CAS end up having some degree of the ABA problem. So I got to thinking. Wouldn't a partially lock-free system be better than always using locks? May some oper...
Hi, In the ARM ABI documentation I come across functions defined like: __value_in_regs struct bar foo(int a, int b) { ... } but GCC(4.3.3) doesn't allow it and all I could find are references to some RealView compiler. Is there any way of doing this from GCC? I have tried -freg-struct-return but it doesn't make a difference. As ...
I have the following code: int main(void) { struct { int x; } a, b; struct { int x; } c; struct { int x; } *p; b = a; /* OK */ c = a; /* Doesn't work */ p = &a; /* Doesn't work */ return 0; } which fails to compile under GCC (3.4.6), with the following error: test.c:8: error: incompatible types in a...
I can't find anywhere what the -all_load flag do when compiling Objective-C code. I have some issues uploading binaries to Apple, the they say it's because I didn't use this flag, but my code compiles even without it. Can some one help me with that? Thanks ...
I'm trying to profile an application I have, but I don't want anything related to the UI (made in wxWidgets) to show up in gprof's callgraph etc. How can I do this? ...