GNOME Terminal Bold Font

Enable bold font for GNOME Terminal:

0x01

# Get profile id
dconf dump /org/gnome/terminal/legacy/
 
# Set bold font
dconf write /org/gnome/terminal/legacy/profiles:/:b1dcc9dd-5262-4d8d-a863-c897e6d979b9/font "'Monospace Bold 14'"

0x02
Preferences->Profiles->->Colors:
Select “Show bold text in bright colors”

Reserved IP addresses

IPv4:

0.0.0.0/8
10.0.0.0/8
100.64.0.0/10
127.0.0.0/8
169.254.0.0/16
172.16.0.0/12
192.0.0.0/24
192.0.2.0/24
192.88.99.0/24
192.168.0.0/16
198.18.0.0/15
198.51.100.0/24
203.0.113.0/24
224.0.0.0/4
240.0.0.0/4
255.255.255.255/32

IPv6:

::/128
::1/128
::ffff:0:0/96
::ffff:0:0:0/96
64:ff9b::/96
100::/64
2001::/32
2001:20::/28
2001:db8::/32
2002::/16
fc00::/7
fe80::/10
ff00::/8

OpenJDK Guide

Java Virtual Machine Guide: https://docs.oracle.com/en/java/javase/11/vm/native-memory-tracking.html#GUID-710CAEA1-7C6D-4D80-AB0C-B0958E329407

HostSpot Virtual Machine Garbage Collection Tuning Guide: https://docs.oracle.com/en/java/javase/11/gctuning/garbage-collector-implementation.html#GUID-23844E39-7499-400C-A579-032B68E53073

OpenJDK Developers’ Guide: https://openjdk.java.net/guide/index.html

HotSpot Runtime Overview: https://openjdk.java.net/groups/hotspot/docs/RuntimeOverview.html

Java Coding Style: https://www.oracle.com/java/technologies/javase/codeconventions-contents.html

HotSpot Coding Style: https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md

HotSpot VM Options: https://www.oracle.com/java/technologies/javase/vmoptions-jsp.html

PrintAssembly: https://wiki.openjdk.java.net/display/HotSpot/PrintAssembly

HotSpot Glossary of Terms: https://openjdk.java.net/groups/hotspot/docs/HotSpotGlossary.html

Building the JDK: https://openjdk.java.net/groups/build/doc/building.html

Building jtreg: http://openjdk.java.net/jtreg/build.html

JVM Allocate Prefetch Options: https://www.opsian.com/blog/jvms-allocateprefetch-options/

Catch exception thrown from memory references

By default an exception can only occur during a function call or a throw. If we needs to catch excpetions thrown from trapping instructions, using the `-fnon-call-exceptions`.

Docs:

-fnon-call-exceptions

Generate code that allows trapping instructions to throw exceptions. Note that this requires platform-specific runtime support that does not exist everywhere. Moreover, it only allows trapping instructions to throw exceptions, i.e. memory references or floating point instructions. It does not allow exceptions to be thrown from arbitrary signal handlers such as SIGALRM. 

Example:

#include <iostream>
 
#include <signal.h>
 
using namespace std;
 
static void
sigsegv_handler (int signo)
{
    throw 0;
}
 
int
main (int argc, char *argv[])
{
    int *ptr = nullptr;
    int res;
 
    signal (SIGSEGV, sigsegv_handler);
 
    try {
        res = *ptr;
    } catch (...) {
        cout << "exception" << endl;
    }
 
    return res;
}
g++ -fnon-call-exceptions -o sig sig.cpp

Refernces:
[1] https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html

Load shared libraries with preferred base address

For performance, sometimes we need to adjust the address space layout. The following way allows the shared or executable object to be loaded with preferred base address.

When the dynamic link maps the shared object, the virtual address of segment(that in ELF program header) will be used as the mapping address hints.

Type 1
Link with text-segment starting address.

# Adjust base address to 0x10000 */
gcc -shared ... -Wl,-Ttext-segment=0x10000

Type 2
We can adjust the virtual address of loaded segment by linker scripts.

0x1 Get link script template

gcc -shared -Wl,--verbose > ld.script

Clear the contents before and after the ‘equal sign’.

0x2 Adjust the base address

....
SECTIONS
{
    /* Adjust base address to 0x10000 */
    . = SEGMENT_START("text-segment", 0x10000) + SIZEOF_HEADERS;
    ...
}
....

0x3 Link with script

gcc -shared ... -Wl,-T ld.script

Over!