Author: peteware

In Trump’s own words

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A Dana Milbank column at The Washington Post is to funny and to sad to bear

A Trump fireside chat — in his own (unfortunate) words

This blindsided the world! Who could have ever predicted a thing like this? This was something that nobody has ever thought could happen to this country.

I’ve always known this is a real, this is a pandemic. I felt it was a pandemic long before it was called a pandemic. I always treated the Chinese Virus very seriously.

It’s a constant stream of contradictions and incoherence.

Walmart, opioids, and Trump administration

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Walmart Was Almost Charged Criminally Over Opioids. Trump Appointees Killed the Indictment.:

Opioids dispensed by Walmart pharmacies in Texas had killed customers who had overdosed. The pharmacists who dispensed those opioids had told the company they didn’t want to fill the prescriptions because they were coming from doctors who were running pill mills. They pleaded for help and guidance from Walmart’s corporate office.

…

Investigators had obtained records of similar cries for help from Walmart pharmacists all over the country: from Maine, North Carolina, Kansas and Washington, and other states. They reported hundreds of thousands of suspicious or inappropriate opioid prescriptions.

…

Before the Texas prosecutors could file their case, however, Walmart escalated concerns to high-ranking officials at the DOJ, who then intervened. Brown was ordered to stand down. On Aug. 31, 2018, Trump officials officially informed Walmart that the DOJ would decline to prosecute the company

Coronavirus: How Long

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The Washington Post has an article projecting what might happen with the Corona virus.

This graph is not infections but rather how many critical-care beds are needed per 100,000 people.

The surprising thing is the timeline. Assuming we do everything there’s a really big peak in September.

Corona Virus Scenarios

Coronavirus: why quarantine?

peteware

The article in OurWorldInData.org has this (symbolic) diagram that shows why it’s important to slow down the rate of infection. It’s not to decrease the number of people infected but rather to keep the healthcare system from being overwhelmed and so causing more deaths.

The horizontal line represents the theoretical capacity of the healthcare system.

Flattening the curve

CppCon 2019: De-Fragmenting C++

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Herb Sutter

  • add things (more); fix things (some); simplify (least);
  • Why not reverse this?
  • adding things (eg MetaClasses) can simplify things

A tale of two compiler switches

-fno-exceptions
-fno-rtti

  • Make things static by default
  • Dynamic by opt-in

Exception Handling

  • isocpp.org 2018-02 survey; 48% ban exceptions either fully or partially (22% not allowed)
  • error codes; expected/outcome types; exceptions
  • std::error_code. std::filesystem supports both dialect

Root cause

  • Today’s exception handling is not zero-overhead. Just enabling increases size
  • throwing an exception not statically boundable space and time overhead. Violates you can’t reasonably write it better by hand
  • Lack of control

Key definition

  • what is a recoverable error
  • A function cannot do what it is supposed to do. Mirriam webster definition of “error”
  • A precondition violation is always a bug in the caller

Four coordinated proposals

  • Enable zero-overhead exception handling
  • throw few exceptions (90% of all exceptions should not be)
  • support explicit try for visble propagation

static exceptions

  • throwing values of static types means by value. No dynamic memory
  • isomorphic to error codes
  • share return channel
  • Need to be backward compatible. Opt in
  • As-if returning union(Success; Error;} + bool
  • doubles down on value semantics

Proposal

  • Add a noexcept-querable allocator proprety for “reports vs aborts” on allocation failure.
  • recommend conditional noexcept based on the relvant allocator
  • babb on GitHub.com/HerbSutter

Part 2: Run-time type information

  • Same for exceptions
  • Joe Bialek Wendesday Root cause of CVEs by patch year.
    • Type confusion increasing (e.g. static downcast)
    • static_cast perhaps because RTTI is banned
  • RTTI allowed in 68%

static_cast down-casts

  • Peter Collingbourne
  • Uses vtable ordered in memory so downcast is just a range check
  • down_cast

    5 instructions

  • fads

CppCon 2019: Modern C++ debugging tools

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Greg Law

gdb

  • ptrace()
  • signals ony reach the tracee via PTRACE_COUNT
  • breakpoints and single step are SIGTRAPs
  • ^C is SIGINT
  • modify instruction causes SIGTRAP

DWARF

g++ -g3??? ; helps make inline functions not look inline; macros

  • “Optomized out” really means it’s just later
  • readelf —dump-debug
  • can actually track registers while live
  • Call frame analysys
  • Catch throw or catch
  • Libthreddb

address Sanitizer

Malloc and free are intercepted. Shadow memory keeps track

Replay

Record and replay nondeterministic steps. Just Re execute to get to current point

Static analysis

What’s The best way for a c++ programmer to make money? Inheritance

Synopsis