For both of these to work the program binary must contain additional debugging information that associates addresses in the program image with locations in the source code (source file and line number.)
To add a breakpoint at a particular line the debugger finds the program address closest to that line, modifies the copy of the executable in memory to insert a special "break" instruction at that location which will cause the program's execution to be interrupted, then "traces" the program's execution and waits for it to reach the breakpoint and stop.
I can't comment for the latest version of gdb - but many debuggers actually swap the assembly instruction at the desired breakpoint location (in memory) with an interrupt instruction. This "wakes up" the debugger which takes control at this point.
GDB is aware of your code : it knows all about it. When you set a breakpoint at a line, GDB gets the equivalant machine instruction address : all your code (as machine instructions) is loaded in memory, so the instructions of your code have an address.
So now GDB knows the adress of the instruction you want to break. When you run your programm, GDB will use ptrace, which allow GDB to "see" each instructions before their execution. Then GDB have just to look if the current instruction (which will be executed) is the same as your instruction (that you want to break).
In my previous column I talked about the ices in Comet ISON's nucleus acting like a glue holding the chunks of dust, dirt, and rock together. As I write this it looks like enough of Comet ISON's ices evaporated as it zipped by the Sun on Thanksgiving to break the nucleus apart into a rubble and dust pile. Comet ISON's nucleus was less than a mile across so there wasn't that much ice available to survive getting within just 683,000 miles of the Sun's surface. Also, the tidal stresses from the Sun's strong gravity at such a close distance stretched the nucleus to the breaking point. There might still be a tail of some sort coming from gas and dust coming off the rubble pile but it won't be visible without a decent telescope on a dark sky.
Although, ISON is essentially gone, it was a great boon to the astronomers who study comets since it was the first comet that was observed from nearly the orbit of Saturn to within a solar radius of the Sun's surface. There was to be a post-perihelion (after closest Sun distance) workshop on December 6th to present what the astronomers had learned since the August Comet ISON Observer's Workshop and plan for post-perihelion observations. Well, most of the post-perihelion observations are out but there will still be plenty to talk about since a comet like ISON comes around once every 200 years. There will be plenty of other comets gracing our skies over the coming years, of course, but a fresh one coming from the Oort Cloud for the first time and getting so close to the Sun is quite rare.
In our evening sky Venus shines at its brightest now as it catches up to Earth in its faster orbit around the Sun. Venus will be the very bright star low in the southwest after sunset. It will be set almost three hours after sunset. Through binoculars you may be able to see Venus as a thin crescent phase. When Venus is near the horizon, its light can get refracted all about to make it appear to change color and brightness quickly, causing it to sometimes be confused with a UFO (of the spacecraft variety). Farther up in the southwest will be a fat Waxing Crescent Moon. First Quarter phase is on Monday.
Brilliant Jupiter rises soon after Venus sets. Jupiter is on the Pollux side of Gemini (bottom edge as seen when Gemini is rising in the northeast). By 8 PM Jupiter and the rest of Gemini should be up high enough to easily see. The two bright stars at the heads of the Gemini twins are Castor and Pollux. As Gemini is rising, Castor is higher up than Pollux and both of them will be to the left of Jupiter. Slightly above Castor as Gemini is rising is the radiant of the Geminid meteor shower. The night of December 13th-14th is the peak of the Geminids with a meteor from the shower visible every minute or so on average on a dark sky far from any city lights. The Moon will be in a Waxing Gibbous phase by then, just three days from Full Phase. Although the radiant of the shower is near Castor, meteors can be seen anywhere in the sky. More meteors will be seen after midnight when the Earth has rotated Kern County to face in the direction of the Earth's orbital motion. Also, after midnight, it will be possible to put the Moon behind you as you face east away from it. The Moon will set around 4:30 AM, so you'll probably spot even more meteors after then. Last year there were quite a number of meteors visible from the shower in the two nights prior to the peak. It will probably do that again and the Moon will set even earlier the nights before December 13/14. Whichever night you decide to observe the meteors, be sure you bundle up with multiple layers!
The Geminids are the dust trail left behind the asteroid 3200 Phaethon which is actually a now-dead comet. All of its volatiles (easily vaporized materials) have long since been boiled away leaving a hunk of rock and dust. The bare rock continues to crack and crumble as passes near the Sun. The Earth passes through Phaethon's dust trail every mid-December. The rock bits hit our atmosphere at about 36 kilometers per second (that's 80,000 miles per hour) and burn up many tens of miles above the surface. As the Earth plows into Phaethon's debris trail, the meteors appear to come from a particular spot in sky, a geometric effect much like the parallel rails of a train track converging at a point in the distance. While you're observing meteors, enjoy the brilliant stars of Orion, Canis Major, Taurus, and Auriga.
Haxtun is in Phillips county in northeast Colorado. It isn't the county seat, nor does it seem to (yet) have any residents who have taken the time to record its history on the Internet. What it is, though, is the northern end of a stretch of highway CO-59 that I've not travelled. So, this would be a trip to Haxtun, and then south along a new bit of road.
I'd be zigzagging west and north, generally heading towards the western Nebraska line. One thing about navigation in Kansas, it doesn't really much matter if you go west then north, or the other way around. When the roads are on the section lines, it's all the same distance.
Great Bend, Kansas was founded in 1871 on the AT&SF not very far from Fort Zarah on the Santa Fe Trail. As you might expect by the name, the Arkansas River has a "great bend" near here, and was a break-away point for wagons along the Santa Fe trail.
Beaver City, Nebraska was founded in 1872 along Beaver Creek. The inventor of Kool-Aid (Edwin Perkins) lived nearby, and he seems to be the most distinguished (nearby) resident (so far). You'll see more towns in Nebraska built around the 'town square' concept than you do in Kansas. Generally, if a town is built on the railroad, it'll be a straightforward grid system. Otherwise, there's a good chance that the town will be laid out with a center square (where the courthouse is hoped to be built).
Palisade, Nebraska was founded in 1879 on the Frenchman River. The location of the town shuffled a bit in order to be adjacent to the Burlington railroad, when it came through. During the 1940s, a POW camp was built for German prisoners (who were used as farm workers).
Ulysses, Kansas was founded in 1885. In 1909, under the financial weight of bonds they could not pay, the whole town moved two miles away and started fresh. Bond holders were left holding the bag (but, probably deserved what they got).
A very large water well was hand-dug for the Santa Fe railroad. For many years, this single attraction was the most famous thing about Greensburg. After the tornado, a new building and museum was built over the "Big Well."
(This review contains copious spoilers: if you intend to read the novel yourself, proceed with caution. We're posting it as a blog since it's not strictly music-related, despite being written by a prominent musician. Now read on!)
Joining the vast array of musicians-turned-novelists (wait, what?), Davey Havok of AFI fame throws his hat into the ring with this, his first book. Pop Kids is inspired by "pop stars, fashion models, celebrities, internet porn, social networking, reality TV, sex, drugs and vegan banana bread", and stars a cast of teenagers with dubious nicknames.
It's always a bold move when artists make the jump from one medium to another, and personally I've always treated the move with a little suspicion, like when Michael Jordan reinvented himself as a baseball player after his first retirement. It's not always a given that talents in one area translate to similar skills in another, and I'm not entirely sure this is the case with Pop Kids.
The first thing that hits you about this novel is the sheer amount of branding. Within the first few pages I was left wondering if the product placement was intentional: McQueen, iPhone, San Pellegrino, Hello Kitty and others are names that occur almost as much as those of the protagonists. Maybe this is Havok's way of highlighting the brand-obsessed youth of today and the commercialised culture that dominates the LA scene, but it becomes particularly wearing as the novel plays on.
Then you have the characters: rarely can I remember reading a book with this many unlikeable creations. It's not that they're all obnoxious ciphers, but mostly that they're paper-thin and two-dimensional, to the point where I could barely summon up the energy to remember who was who after yet another exhausting chapter of references to "MK", "Score", "Lynch" and other self-created nicknames (do you know anybody who successfully made their own nickname work?). The protagonist's constant references to veganism and straight edge were both twee and proselytising in equal measures: either we get saccharine lines like "a fresh, locally baked low-fat cranberry scone from Cherie Cherie is waiting for me in the breadbox", or we get preachy asides like "my guests begin poisoning their minds and bodies [with alcohol]". Havok has said in promotional material that Score, the lead character, is not meant to represent the author, but it's hard to not take this view the more these references are shoehorned in.
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