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| author | johannst <johannst@users.noreply.github.com> | 2023-05-29 20:34:16 +0000 |
|---|---|---|
| committer | johannst <johannst@users.noreply.github.com> | 2023-05-29 20:34:16 +0000 |
| commit | eaad036407c9546be0de27f61745fef4b6856e56 (patch) | |
| tree | c270e3fbc87f3b7c9fc25ac60f4f8f611962de5e /print.html | |
| parent | 87c538b89ea68cf0c133a9243097ffac646e6739 (diff) | |
| download | notes-eaad036407c9546be0de27f61745fef4b6856e56.tar.gz notes-eaad036407c9546be0de27f61745fef4b6856e56.zip | |
deploy: d2013ee5952bbcf88906a832748783e372f3a939
Diffstat (limited to 'print.html')
| -rw-r--r-- | print.html | 283 |
1 files changed, 277 insertions, 6 deletions
@@ -84,7 +84,7 @@ <nav id="sidebar" class="sidebar" aria-label="Table of contents"> <div class="sidebar-scrollbox"> - <ol class="chapter"><li class="chapter-item expanded affix "><a href="intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="tools/index.html"><strong aria-hidden="true">1.</strong> Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="tools/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="tools/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="tools/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li><li class="chapter-item expanded "><a href="tools/tmux.html"><strong aria-hidden="true">1.4.</strong> tmux</a></li><li class="chapter-item expanded "><a href="tools/git.html"><strong aria-hidden="true">1.5.</strong> git</a></li><li class="chapter-item expanded "><a href="tools/awk.html"><strong aria-hidden="true">1.6.</strong> awk</a></li><li class="chapter-item expanded "><a href="tools/emacs.html"><strong aria-hidden="true">1.7.</strong> emacs</a></li><li class="chapter-item expanded "><a href="tools/gpg.html"><strong aria-hidden="true">1.8.</strong> gpg</a></li><li class="chapter-item expanded "><a href="tools/gdb.html"><strong aria-hidden="true">1.9.</strong> gdb</a></li><li class="chapter-item expanded "><a href="tools/gdbserver.html"><strong aria-hidden="true">1.10.</strong> gdbserver</a></li><li class="chapter-item expanded "><a href="tools/radare2.html"><strong aria-hidden="true">1.11.</strong> radare2</a></li><li class="chapter-item expanded "><a href="tools/qemu.html"><strong aria-hidden="true">1.12.</strong> qemu</a></li><li class="chapter-item expanded "><a href="tools/pacman.html"><strong aria-hidden="true">1.13.</strong> pacman</a></li><li class="chapter-item expanded "><a href="tools/dot.html"><strong aria-hidden="true">1.14.</strong> dot</a></li></ol></li><li class="chapter-item expanded "><a href="monitor/index.html"><strong aria-hidden="true">2.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="monitor/lsof.html"><strong aria-hidden="true">2.1.</strong> lsof</a></li><li class="chapter-item expanded "><a href="monitor/ss.html"><strong aria-hidden="true">2.2.</strong> ss</a></li><li class="chapter-item expanded "><a href="monitor/pidstat.html"><strong aria-hidden="true">2.3.</strong> pidstat</a></li><li class="chapter-item expanded "><a href="monitor/pgrep.html"><strong aria-hidden="true">2.4.</strong> pgrep</a></li><li class="chapter-item expanded "><a href="monitor/pmap.html"><strong aria-hidden="true">2.5.</strong> pmap</a></li><li class="chapter-item expanded "><a href="monitor/pstack.html"><strong aria-hidden="true">2.6.</strong> pstack</a></li></ol></li><li class="chapter-item expanded "><a href="trace_profile/index.html"><strong aria-hidden="true">3.</strong> Trace and Profile</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="trace_profile/strace.html"><strong aria-hidden="true">3.1.</strong> strace</a></li><li class="chapter-item expanded "><a href="trace_profile/ltrace.html"><strong aria-hidden="true">3.2.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="trace_profile/perf.html"><strong aria-hidden="true">3.3.</strong> perf</a></li><li class="chapter-item expanded "><a href="trace_profile/oprofile.html"><strong aria-hidden="true">3.4.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="trace_profile/time.html"><strong aria-hidden="true">3.5.</strong> time</a></li></ol></li><li class="chapter-item expanded "><a href="binary/index.html"><strong aria-hidden="true">4.</strong> Binary</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="binary/od.html"><strong aria-hidden="true">4.1.</strong> od</a></li><li class="chapter-item expanded "><a href="binary/xxd.html"><strong aria-hidden="true">4.2.</strong> xxd</a></li><li class="chapter-item expanded "><a href="binary/readelf.html"><strong aria-hidden="true">4.3.</strong> readelf</a></li><li class="chapter-item expanded "><a href="binary/objdump.html"><strong aria-hidden="true">4.4.</strong> objdump</a></li><li class="chapter-item expanded "><a href="binary/nm.html"><strong aria-hidden="true">4.5.</strong> nm</a></li></ol></li><li class="chapter-item expanded "><a href="development/index.html"><strong aria-hidden="true">5.</strong> Development</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="development/c++filt.html"><strong aria-hidden="true">5.1.</strong> c++filt</a></li><li class="chapter-item expanded "><a href="development/c++.html"><strong aria-hidden="true">5.2.</strong> c++</a></li><li class="chapter-item expanded "><a href="development/glibc.html"><strong aria-hidden="true">5.3.</strong> glibc</a></li><li class="chapter-item expanded "><a href="development/gcc.html"><strong aria-hidden="true">5.4.</strong> gcc</a></li><li class="chapter-item expanded "><a href="development/make.html"><strong aria-hidden="true">5.5.</strong> make</a></li><li class="chapter-item expanded "><a href="development/ld.so.html"><strong aria-hidden="true">5.6.</strong> ld.so</a></li><li class="chapter-item expanded "><a href="development/symbolver.html"><strong aria-hidden="true">5.7.</strong> symbol versioning</a></li><li class="chapter-item expanded "><a href="development/python.html"><strong aria-hidden="true">5.8.</strong> python</a></li></ol></li><li class="chapter-item expanded "><a href="linux/index.html"><strong aria-hidden="true">6.</strong> Linux</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="linux/systemd.html"><strong aria-hidden="true">6.1.</strong> systemd</a></li><li class="chapter-item expanded "><a href="linux/coredump.html"><strong aria-hidden="true">6.2.</strong> coredump</a></li><li class="chapter-item expanded "><a href="linux/ptrace_scope.html"><strong aria-hidden="true">6.3.</strong> ptrace_scope</a></li><li class="chapter-item expanded "><a href="linux/cryptsetup.html"><strong aria-hidden="true">6.4.</strong> cryptsetup</a></li><li class="chapter-item expanded "><a href="linux/swap.html"><strong aria-hidden="true">6.5.</strong> swap</a></li><li class="chapter-item expanded "><a href="linux/input.html"><strong aria-hidden="true">6.6.</strong> input</a></li></ol></li><li class="chapter-item expanded "><a href="network/index.html"><strong aria-hidden="true">7.</strong> Network</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="network/tcpdump.html"><strong aria-hidden="true">7.1.</strong> tcpdump</a></li><li class="chapter-item expanded "><a href="network/firewall-cmd.html"><strong aria-hidden="true">7.2.</strong> firewall-cmd</a></li><li class="chapter-item expanded "><a href="network/nftables.html"><strong aria-hidden="true">7.3.</strong> nftables</a></li></ol></li><li class="chapter-item expanded "><a href="web/index.html"><strong aria-hidden="true">8.</strong> Web</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="web/html.html"><strong aria-hidden="true">8.1.</strong> html</a></li><li class="chapter-item expanded "><a href="web/chartjs.html"><strong aria-hidden="true">8.2.</strong> chartjs</a></li></ol></li><li class="chapter-item expanded "><a href="arch/index.html"><strong aria-hidden="true">9.</strong> Arch</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="arch/x86_64.html"><strong aria-hidden="true">9.1.</strong> x86_64</a></li><li class="chapter-item expanded "><a href="arch/arm64.html"><strong aria-hidden="true">9.2.</strong> arm64</a></li><li class="chapter-item expanded "><a href="arch/armv7.html"><strong aria-hidden="true">9.3.</strong> armv7</a></li><li class="chapter-item expanded "><a href="arch/riscv.html"><strong aria-hidden="true">9.4.</strong> riscv</a></li></ol></li></ol> + <ol class="chapter"><li class="chapter-item expanded affix "><a href="intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="tools/index.html"><strong aria-hidden="true">1.</strong> Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="tools/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="tools/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="tools/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li><li class="chapter-item expanded "><a href="tools/tmux.html"><strong aria-hidden="true">1.4.</strong> tmux</a></li><li class="chapter-item expanded "><a href="tools/git.html"><strong aria-hidden="true">1.5.</strong> git</a></li><li class="chapter-item expanded "><a href="tools/awk.html"><strong aria-hidden="true">1.6.</strong> awk</a></li><li class="chapter-item expanded "><a href="tools/emacs.html"><strong aria-hidden="true">1.7.</strong> emacs</a></li><li class="chapter-item expanded "><a href="tools/gpg.html"><strong aria-hidden="true">1.8.</strong> gpg</a></li><li class="chapter-item expanded "><a href="tools/gdb.html"><strong aria-hidden="true">1.9.</strong> gdb</a></li><li class="chapter-item expanded "><a href="tools/gdbserver.html"><strong aria-hidden="true">1.10.</strong> gdbserver</a></li><li class="chapter-item expanded "><a href="tools/radare2.html"><strong aria-hidden="true">1.11.</strong> radare2</a></li><li class="chapter-item expanded "><a href="tools/qemu.html"><strong aria-hidden="true">1.12.</strong> qemu</a></li><li class="chapter-item expanded "><a href="tools/pacman.html"><strong aria-hidden="true">1.13.</strong> pacman</a></li><li class="chapter-item expanded "><a href="tools/dot.html"><strong aria-hidden="true">1.14.</strong> dot</a></li></ol></li><li class="chapter-item expanded "><a href="monitor/index.html"><strong aria-hidden="true">2.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="monitor/lsof.html"><strong aria-hidden="true">2.1.</strong> lsof</a></li><li class="chapter-item expanded "><a href="monitor/ss.html"><strong aria-hidden="true">2.2.</strong> ss</a></li><li class="chapter-item expanded "><a href="monitor/pidstat.html"><strong aria-hidden="true">2.3.</strong> pidstat</a></li><li class="chapter-item expanded "><a href="monitor/pgrep.html"><strong aria-hidden="true">2.4.</strong> pgrep</a></li><li class="chapter-item expanded "><a href="monitor/pmap.html"><strong aria-hidden="true">2.5.</strong> pmap</a></li><li class="chapter-item expanded "><a href="monitor/pstack.html"><strong aria-hidden="true">2.6.</strong> pstack</a></li></ol></li><li class="chapter-item expanded "><a href="trace_profile/index.html"><strong aria-hidden="true">3.</strong> Trace and Profile</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="trace_profile/strace.html"><strong aria-hidden="true">3.1.</strong> strace</a></li><li class="chapter-item expanded "><a href="trace_profile/ltrace.html"><strong aria-hidden="true">3.2.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="trace_profile/perf.html"><strong aria-hidden="true">3.3.</strong> perf</a></li><li class="chapter-item expanded "><a href="trace_profile/oprofile.html"><strong aria-hidden="true">3.4.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="trace_profile/time.html"><strong aria-hidden="true">3.5.</strong> time</a></li></ol></li><li class="chapter-item expanded "><a href="binary/index.html"><strong aria-hidden="true">4.</strong> Binary</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="binary/od.html"><strong aria-hidden="true">4.1.</strong> od</a></li><li class="chapter-item expanded "><a href="binary/xxd.html"><strong aria-hidden="true">4.2.</strong> xxd</a></li><li class="chapter-item expanded "><a href="binary/readelf.html"><strong aria-hidden="true">4.3.</strong> readelf</a></li><li class="chapter-item expanded "><a href="binary/objdump.html"><strong aria-hidden="true">4.4.</strong> objdump</a></li><li class="chapter-item expanded "><a href="binary/nm.html"><strong aria-hidden="true">4.5.</strong> nm</a></li></ol></li><li class="chapter-item expanded "><a href="development/index.html"><strong aria-hidden="true">5.</strong> Development</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="development/c++filt.html"><strong aria-hidden="true">5.1.</strong> c++filt</a></li><li class="chapter-item expanded "><a href="development/c++.html"><strong aria-hidden="true">5.2.</strong> c++</a></li><li class="chapter-item expanded "><a href="development/glibc.html"><strong aria-hidden="true">5.3.</strong> glibc</a></li><li class="chapter-item expanded "><a href="development/gcc.html"><strong aria-hidden="true">5.4.</strong> gcc</a></li><li class="chapter-item expanded "><a href="development/make.html"><strong aria-hidden="true">5.5.</strong> make</a></li><li class="chapter-item expanded "><a href="development/ld.so.html"><strong aria-hidden="true">5.6.</strong> ld.so</a></li><li class="chapter-item expanded "><a href="development/symbolver.html"><strong aria-hidden="true">5.7.</strong> symbol versioning</a></li><li class="chapter-item expanded "><a href="development/python.html"><strong aria-hidden="true">5.8.</strong> python</a></li><li class="chapter-item expanded "><a href="development/gcov.html"><strong aria-hidden="true">5.9.</strong> gcov</a></li></ol></li><li class="chapter-item expanded "><a href="linux/index.html"><strong aria-hidden="true">6.</strong> Linux</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="linux/systemd.html"><strong aria-hidden="true">6.1.</strong> systemd</a></li><li class="chapter-item expanded "><a href="linux/coredump.html"><strong aria-hidden="true">6.2.</strong> coredump</a></li><li class="chapter-item expanded "><a href="linux/ptrace_scope.html"><strong aria-hidden="true">6.3.</strong> ptrace_scope</a></li><li class="chapter-item expanded "><a href="linux/cryptsetup.html"><strong aria-hidden="true">6.4.</strong> cryptsetup</a></li><li class="chapter-item expanded "><a href="linux/swap.html"><strong aria-hidden="true">6.5.</strong> swap</a></li><li class="chapter-item expanded "><a href="linux/input.html"><strong aria-hidden="true">6.6.</strong> input</a></li></ol></li><li class="chapter-item expanded "><a href="network/index.html"><strong aria-hidden="true">7.</strong> Network</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="network/tcpdump.html"><strong aria-hidden="true">7.1.</strong> tcpdump</a></li><li class="chapter-item expanded "><a href="network/firewall-cmd.html"><strong aria-hidden="true">7.2.</strong> firewall-cmd</a></li><li class="chapter-item expanded "><a href="network/nftables.html"><strong aria-hidden="true">7.3.</strong> nftables</a></li></ol></li><li class="chapter-item expanded "><a href="web/index.html"><strong aria-hidden="true">8.</strong> Web</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="web/html.html"><strong aria-hidden="true">8.1.</strong> html</a></li><li class="chapter-item expanded "><a href="web/chartjs.html"><strong aria-hidden="true">8.2.</strong> chartjs</a></li></ol></li><li class="chapter-item expanded "><a href="arch/index.html"><strong aria-hidden="true">9.</strong> Arch</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="arch/x86_64.html"><strong aria-hidden="true">9.1.</strong> x86_64</a></li><li class="chapter-item expanded "><a href="arch/arm64.html"><strong aria-hidden="true">9.2.</strong> arm64</a></li><li class="chapter-item expanded "><a href="arch/armv7.html"><strong aria-hidden="true">9.3.</strong> armv7</a></li><li class="chapter-item expanded "><a href="arch/riscv.html"><strong aria-hidden="true">9.4.</strong> riscv</a></li></ol></li></ol> </div> <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div> </nav> @@ -2618,6 +2618,7 @@ objdump -D -b binary -m i386:x86-64 test-bin <li><a href="development/./ld.so.html">ld.so</a></li> <li><a href="development/./symbolver.html">symbol versioning</a></li> <li><a href="development/./python.html">python</a></li> +<li><a href="development/./gcov.html">gcov</a></li> </ul> <div style="break-before: page; page-break-before: always;"></div><h1 id="cfilt1"><a class="header" href="#cfilt1">c++filt(1)</a></h1> <h2 id="demangle-symbol"><a class="header" href="#demangle-symbol">Demangle symbol</a></h2> @@ -2628,6 +2629,7 @@ objdump -D -b binary -m i386:x86-64 test-bin <pre><code class="language-markdown"> readelf -W --dyn-syms <elf> | c++filt </code></pre> <div style="break-before: page; page-break-before: always;"></div><h1 id="c"><a class="header" href="#c">c++</a></h1> +<p>Source files of most examples is available <a href="https://github.com/johannst/notes/tree/master/src/development/c%2B%2B">here</a>.</p> <h2 id="type-deduction"><a class="header" href="#type-deduction">Type deduction</a></h2> <p>Force compile error to see what <code>auto</code> is deduced to.</p> <pre><code class="language-cpp">auto foo = bar(); @@ -2673,6 +2675,74 @@ int main() { show(1, 1.0, "foo", 'a'); } </code></pre> +<h2 id="forwarding-reference-fwd-ref"><a class="header" href="#forwarding-reference-fwd-ref">Forwarding reference (<a href="https://en.cppreference.com/w/cpp/language/reference#Forwarding_references">fwd ref</a>)</a></h2> +<p>A <code>forwarding reference</code> is a special references that preserves the <code>value category</code> of a function parameter and therefore allows for <code>perfect</code> +forwarding.</p> +<p>A forwarding reference is a parameter of a function template, which is declared +as <code>rvalue</code> reference to a <code>non-cv</code> qualified <code>type</code> template parameter.</p> +<pre><code class="language-cpp">template<typename T> +void fn(T&& param); // param is a forwarding reference +</code></pre> +<p>Perfect forwarding can be achieved with <a href="https://en.cppreference.com/w/cpp/utility/forward"><code>std::forward</code></a>. This for +example allows a wrapper function to pass a parameter with the <strong>exact</strong> same +value category to a down-stream function which is being invoked in the wrapper.</p> +<pre><code class="language-cpp">#include <cstdio> +#include <utility> + +struct M {}; + +// -- CONSUMER ----------------------------------------------------------------- + +void use(M&) { + puts(__PRETTY_FUNCTION__); +} + +void use(M&&) { + puts(__PRETTY_FUNCTION__); +} + +// -- TESTER ------------------------------------------------------------------- + +template<typename T> +void wrapper(T&& param) { // forwarding reference + puts(__PRETTY_FUNCTION__); + // PARAM is an lvalue, therefore this always calls use(M&). + use(param); +} + +template<typename T> +void fwd_wrapper(T&& param) { // forwarding reference + puts(__PRETTY_FUNCTION__); + // PARAM is an lvalue, but std::forward returns PARAM with the same value + // category as the forwarding reference takes. + use(std::forward<T>(param)); +} + +// -- MAIN --------------------------------------------------------------------- + +int main() { + { + std::puts("==> wrapper rvalue reference"); + wrapper(M{}); + // calls use(M&). + + std::puts("==> wrapper lvalue reference"); + struct M m; + wrapper(m); + // calls use(M&). + } + { + std::puts("==> fwd_wrapper rvalue reference"); + fwd_wrapper(M{}); + // calls use(M&&). + + std::puts("==> fwd_wrapper lvalue reference"); + struct M m; + fwd_wrapper(m); + // calls use(M&). + } +} +</code></pre> <h2 id="example-any_of-template-meta-function"><a class="header" href="#example-any_of-template-meta-function">Example: <code>any_of</code> template meta function</a></h2> <pre><code class="language-cpp">#include <type_traits> @@ -2755,7 +2825,9 @@ void Invoke(const Ctx& C, P... params) { // Custom context. struct Ctx { - void out(const char* s, unsigned v) const { printf("%s%x\n", s, v); } + void out(const char* s, unsigned v) const { + printf("%s%x\n", s, v); + } }; // Operations to invoke. @@ -2766,7 +2838,9 @@ struct OpA { using Return = int; static constexpr const char* const Name = "OpA"; - constexpr Return operator()(int a, int b) const { return a + b; } + constexpr Return operator()(int a, int b) const { + return a + b; + } }; template<typename Ctx> @@ -2775,7 +2849,9 @@ struct OpB { using Return = void; static constexpr const char* const Name = "OpB"; - Return operator()(const Ctx& C, unsigned a) const { C.out("a = ", a); } + Return operator()(const Ctx& C, unsigned a) const { + C.out("a = ", a); + } }; int main() { @@ -2812,7 +2888,9 @@ struct registry { return r.second; } - R invoke(const std::string& nm, P... p) const { return invoke_impl<R>(nm, p...); } + R invoke(const std::string& nm, P... p) const { + return invoke_impl<R>(nm, p...); + } void dump() const { for (const auto& it : m_fns) { @@ -3074,6 +3152,88 @@ int main() { // * No specialization matches, take the primary template. } </code></pre> +<h1 id="example-perfect-forwarding"><a class="header" href="#example-perfect-forwarding">Example: Perfect forwarding</a></h1> +<pre><code class="language-cpp">#include <cassert> +#include <cstdio> +#include <new> +#include <type_traits> +#include <utility> + +struct S {}; + +struct M { + M() { + std::puts("M()"); + } + M(const M&) { + std::puts("M(M&)"); + } + M(M&&) { + std::puts("M(M&&)"); + } + M& operator=(const M&) = delete; + M& operator=(M&&) = delete; + + M(S&, int) { + std::puts("M(S&)"); + } + M(S&&, int) { + std::puts("M(S&&)"); + } + ~M() { + std::puts("~M()"); + } +}; + +template<typename T> +struct option { + static_assert(!std::is_reference_v<T>); + + constexpr option() = default; + + template<typename... Params> + constexpr option(Params&&... params) : m_has_val(true) { + // BAD: does not perfectly forward! + // eg, if option(S&&) is invoked, this would invoke M(S&). + // new (&m_val) T(params...); + + // GOOD: perfectly forwards params to constructor of T. + new (m_val) T(std::forward<Params>(params)...); + } + + ~option() { + reset(); + } + + constexpr T& value() { + assert(m_has_val); + return *reinterpret_cast<T*>(m_val); + } + + private: + constexpr void reset() { + if (!m_has_val) { + return; + } + if constexpr (!std::is_trivially_destructible_v<T>) { + value().~T(); + }; + } + + alignas(T) char m_val[sizeof(T)]; + bool m_has_val{false}; +}; + +int main() { + std::puts("==> case 1"); + // invokes M(S&&, int) + option<M> opt1(S{}, 123); + + std::puts("==> case 2"); + // invokes M() + M(M&&) + option<M> x /* option(M&&) + M(M&&) */ = M{} /* M() */; +} +</code></pre> <div style="break-before: page; page-break-before: always;"></div><h1 id="glibc"><a class="header" href="#glibc">glibc</a></h1> <h2 id="malloc-tracer-mtrace3"><a class="header" href="#malloc-tracer-mtrace3">malloc tracer <a href="http://man7.org/linux/man-pages/man3/mtrace.3.html"><code>mtrace(3)</code></a></a></h2> <p>Trace memory allocation and de-allocation to detect memory leaks. @@ -3115,6 +3275,8 @@ LD_PRELOAD=./libmtrace.so <binary> <li><code>-dM</code> list only <code>#define</code> statements</li> <li><code>-###</code> dry-run, outputting exact compiler/linker invocations</li> <li><code>-print-multi-lib</code> print available multilib configurations</li> +<li><code>--help=<class></code> print description of cmdline options for given class, eg +<code>warnings</code>, <code>optimizers</code>, <code>target</code>, <code>c</code>, <code>c++</code></li> </ul> <h3 id="target-options"><a class="header" href="#target-options">Target options</a></h3> <pre><code class="language-bash"># List all target options with their description. @@ -3123,6 +3285,15 @@ gcc --help=target # Configure for current cpu arch and query (-Q) value of options. gcc -march=native -Q --help=target </code></pre> +<h3 id="warnings--optimizations"><a class="header" href="#warnings--optimizations">Warnings / optimizations</a></h3> +<pre><code class="language-bash"># List available warnings with short description. +gcc --help=warnings +# List available optimizations with short description. +gcc --help=optimizers + +# Prepend --help with `-Q` to print wheter options are enabled or disabled +# instead showing their description. +</code></pre> <h2 id="builtins"><a class="header" href="#builtins"><a href="https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html">Builtins</a></a></h2> <h3 id="__builtin_expectexpr-cond"><a class="header" href="#__builtin_expectexpr-cond"><code>__builtin_expect(expr, cond)</code></a></h3> <p>Give the compiler a hint which branch is hot, so it can lay out the code @@ -3220,7 +3391,7 @@ aaa: bbb: </code></pre> <p>Running above <code>Makefile</code> gives:</p> -<pre><code class="language-test">@ = foobar +<pre><code class="language-text">@ = foobar < = aaa ^ = aaa bbb + = aaa bbb bbb @@ -3237,6 +3408,19 @@ bbb: <ul> <li><code>$(CURDIR)</code>: Path of current working dir after using <code>make -C path</code></li> </ul> +<h2 id="arguments"><a class="header" href="#arguments">Arguments</a></h2> +<p>Arguments specified on the command line <em>override</em> ordinary variable +assignments in the makefile (<a href="https://www.gnu.org/software/make/manual/html_node/Overriding.html">overriding variables</a>).</p> +<pre><code class="language-make">VAR = abc +all: + @echo VAR=$(VAR) +</code></pre> +<pre><code class="language-text"># make +VAR=abc + +# make VAR=123 +VAR=123 +</code></pre> <h2 id="useful-functions"><a class="header" href="#useful-functions">Useful functions</a></h2> <h3 id="substitution-references"><a class="header" href="#substitution-references">Substitution references</a></h3> <p>Substitute strings matching pattern in a list.</p> @@ -3673,6 +3857,93 @@ def sum(a: int, b: int) -> int: <p>Micro benchmarking.</p> <pre><code class="language-bash">python -m timeit '[x.strip() for x in ["a ", " b"]]' </code></pre> +<div style="break-before: page; page-break-before: always;"></div><h1 id="gcov1"><a class="header" href="#gcov1">gcov(1)</a></h1> +<p>Generate code coverage reports in text format.</p> +<p>Compile the source files of interest and link the final binary with the +following flags:</p> +<ul> +<li><code>-fprofile-arcs</code> instruments the generated code such that it writes a <code>.gcda</code> +file when being executed with details about which branches are taken</li> +<li><code>-ftest-coverage</code> writes a <code>.gcno</code> notes file which is used by <code>gcov</code> during +generation of the coverage report</li> +</ul> +<p>Depending on the build environment one may also set <code>-fprofile-abs-path</code> to +generate absolute path names into the <code>.gcno</code> note files, this can ease setups +where compilations are done in different directories to the source directory.</p> +<blockquote> +<p><code>gcc</code> / <code>clang</code> also support an alias flag <code>--coverage</code> which during +compilation time is equivalent to <code>-fprofile-arcs -ftest-coverage</code> and during +link time <code>-lgcov</code>.</p> +</blockquote> +<p>After running the instrumented binary, the human readable report can then be +generated for a single file for example such as</p> +<pre><code class="language-shell">gcov <SRC FILE | OBJ FILE> +</code></pre> +<h2 id="example-6"><a class="header" href="#example-6">Example</a></h2> +<pre><code class="language-cpp">#include <cstdio> + +void tell_me(int desc) { + if (desc & 1) { + std::puts("this"); + } else { + std::puts("that"); + } +} + +int main(int argc, char *argv[]) { + tell_me(argc); + tell_me(argc); + return 0; +} +</code></pre> +<p>The <code>gcov</code> coverage report can be generated as follows for <code>gcc</code> or <code>clang</code>.</p> +<pre><code class="language-make">CXXFLAGS = -fprofile-arcs -ftest-coverage +# or the alias +#CXXFLAGS = --coverage + +cov-gcc: clean + g++ $(CXXFLAGS) -c -o cov.o cov.cc + g++ $(CXXFLAGS) -o $@ cov.o + ./$@ + gcov --demangled-names cov.cc + cat cov.cc.gcov +.PHONY: cov-gcc + +cov-clang: clean + clang++ $(CXXFLAGS) -c -o cov.o cov.cc + clang++ $(CXXFLAGS) -o $@ cov.o + ./$@ + llvm-cov gcov --demangled-names cov.cc + cat cov.cc.gcov +.PHONY: cov-clang + +clean: + $(RM) *.gcov *.gcno *.gcda *.o cov-* +</code></pre> +<p>The will generate a report similar to the following.</p> +<pre><code class="language-text">cat cov.cc.gcov + -: 0:Source:cov.cc + -: 0:Graph:cov.gcno + -: 0:Data:cov.gcda + -: 0:Runs:1 + -: 1:// Copyright (C) 2023 johannst + -: 2: + -: 3:#include <cstdio> + -: 4: + 2: 5:void tell_me(int desc) { + 2: 6: if (desc & 1) { + 2: 7: std::puts("this"); + -: 8: } else { + #####: 9: std::puts("that"); + -: 10: } + 2: 11:} + -: 12: + 1: 13:int main(int argc, char *argv[]) { + 1: 14: tell_me(argc); + 1: 15: tell_me(argc); + 1: 16: return 0; + -: 17:} +</code></pre> <div style="break-before: page; page-break-before: always;"></div><h1 id="linux"><a class="header" href="#linux">Linux</a></h1> <ul> <li><a href="linux/./systemd.html">systemd</a></li> |