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authorjohannst <johannst@users.noreply.github.com>2024-04-10 19:37:02 +0000
committerjohannst <johannst@users.noreply.github.com>2024-04-10 19:37:02 +0000
commit269caa8ae18eb33e1286e4c21d434ea07228a619 (patch)
treeb9c0ae7bf44a6873adc4c9da9204de2bdf4a1de1 /print.html
parent92fc0e8e46352a593c3ce7f87292ee1c4ee4c4e4 (diff)
downloadnotes-269caa8ae18eb33e1286e4c21d434ea07228a619.tar.gz
notes-269caa8ae18eb33e1286e4c21d434ea07228a619.zip
deploy: ae498864bb638e597b589c52ff27237835625281
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diff --git a/print.html b/print.html
index b12601f..2e481d9 100644
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@@ -1095,6 +1095,11 @@ list-keys -t vi-copy list keymaps for vi-copy mode
| remote repository |
+-------------------+
</code></pre>
+<h2 id="config"><a class="header" href="#config">Config</a></h2>
+<pre><code class="language-markdown"> git config --list --show-origin ..... list currently set configs and where
+ they are coming from
+ git --edit [--global] ............... open config in editor (local or global)
+</code></pre>
<h2 id="clean"><a class="header" href="#clean">Clean</a></h2>
<pre><code class="language-markdown"> git clean -X ......... remove only ignored files (-n for dry run)
git clean -f -d -x ... remove untracked &amp; ignored files / folders
@@ -4201,6 +4206,110 @@ static_assert(!is_valid&lt;B&gt;::value, "is false");
</blockquote>
<p>A more detailed description is available in the SO discussion <a href="https://stackoverflow.com/a/27688405">How does
<code>void_t</code> work</a>.</p>
+<h2 id="example-concepts-since-c20"><a class="header" href="#example-concepts-since-c20">Example: Concepts since c++20</a></h2>
+<pre><code class="language-cpp">// REQUIRES EXPRESSION
+// requires { requirement-seq }
+// requires ( parameter-list ) { requirement-seq }
+//
+// [1] https://en.cppreference.com/w/cpp/language/requires
+// [2] https://en.cppreference.com/w/cpp/language/constraints#Constraints
+//
+// REQUIREMENT CLAUSE
+// Not the same as a REQUIREMENT EXPRESSIONS, and is used to require
+// constraints (express concept bounds).
+//
+// [1] https://en.cppreference.com/w/cpp/language/constraints#Requires_clauses
+
+// -- HELPER -------------------------------------------------------------------
+
+template&lt;typename T&gt;
+using Alias = T;
+
+void print(int);
+
+// -- CONCEPTS &amp; REQUIRE EXPRESSIONS -------------------------------------------
+
+// Simple concept from a type trait.
+template&lt;typename T, typename U&gt;
+concept Same = std::is_same&lt;T, U&gt;::value;
+
+// Simple requirement concepts.
+template&lt;typename T&gt;
+concept TraitAddAndPrint = requires(T t, int i) {
+ // Adding T + int must be supported.
+ t + i;
+ // Calling print(T) must be available.
+ print(t);
+};
+
+// Type requirement concepts.
+template&lt;typename T&gt;
+concept TraitTypes = requires(T t) {
+ // T must have a type definition inner.
+ typename T::inner;
+ // Type alias must exist.
+ typename Alias&lt;T&gt;;
+};
+
+// Compound requirement concepts.
+template&lt;typename T&gt;
+concept TraitFns = requires(T t, const T c) {
+ // void T::foo() must exist.
+ { t.foo() };
+ // bool T::bar() const; must exist.
+ { c.bar() } -&gt; Same&lt;bool&gt;;
+ // static void T::stat(); must exist.
+ { T::stat() } -&gt; Same&lt;int&gt;;
+};
+
+// Nested requirement concepts.
+template&lt;typename T&gt;
+concept TraitNested = requires(T t) {
+ // Must satisfy other concepts.
+ requires TraitTypes&lt;T&gt;;
+ requires TraitFns&lt;T&gt;;
+};
+
+// -- REQUIRE EXPRESSIONS ------------------------------------------------------
+
+// Require expressions can be evaluated to booleans.
+template&lt;typename T&gt;
+static constexpr bool IsTraitFns = requires { requires TraitFns&lt;T&gt;; };
+
+// Require expressions can also be used in static assertions.
+static_assert(requires { requires Same&lt;int, int&gt;; });
+static_assert(!requires {
+ typename Alias&lt;int&gt;;
+ requires Same&lt;int, void&gt;;
+});
+
+// -- TESTS --------------------------------------------------------------------
+
+static_assert(requires { requires TraitAddAndPrint&lt;int&gt;; });
+
+struct FnTypeGood {
+ using inner = int;
+};
+struct FnTypeBad {};
+static_assert(requires { requires TraitTypes&lt;FnTypeGood&gt;; });
+static_assert(!requires { requires TraitTypes&lt;FnTypeBad&gt;; });
+
+struct FnGood {
+ void foo();
+ bool bar() const;
+ static int stat();
+};
+struct FnBad {};
+static_assert(requires { requires TraitFns&lt;FnGood&gt;; });
+static_assert(!requires { requires TraitFns&lt;FnBad&gt;; });
+
+struct NestedGood : FnTypeGood, FnGood {};
+struct NestedBad1 : FnGood {};
+struct NestedBad2 : FnTypeGood {};
+static_assert(requires { requires TraitNested&lt;NestedGood&gt;; });
+static_assert(!requires { requires TraitNested&lt;NestedBad1&gt;; });
+static_assert(!requires { requires TraitNested&lt;NestedBad2&gt;; });
+</code></pre>
<h2 id="template-selection-with-partially--fully-specializations"><a class="header" href="#template-selection-with-partially--fully-specializations">Template selection with partially / fully specializations.</a></h2>
<pre><code class="language-cpp">enum Kind {
kPrimary,
@@ -4274,7 +4383,7 @@ 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>
+<h2 id="example-perfect-forwarding"><a class="header" href="#example-perfect-forwarding">Example: Perfect forwarding</a></h2>
<pre><code class="language-cpp">#include &lt;cassert&gt;
#include &lt;cstdio&gt;
#include &lt;new&gt;
@@ -4921,6 +5030,9 @@ symbol=default_main; lookup in file=/usr/lib/libc.so.6 [0]
symbol=default_main; lookup in file=/lib64/ld-linux-x86-64.so.2 [0]
./main: error: symbol lookup error: undefined symbol: default_main (fatal)
</code></pre>
+<h2 id="load-lib-with-same-name-from-different-locations"><a class="header" href="#load-lib-with-same-name-from-different-locations">Load lib with same name from different locations</a></h2>
+<p>The sources in <a href="https://github.com/johannst/notes/tree/master/src/development/ldso/samename">ldso/samename</a> show some experiments, loading the
+libs with the same name but potentially from different locations (paths).</p>
<h2 id="dynamic-linking-x86_64"><a class="header" href="#dynamic-linking-x86_64">Dynamic Linking (x86_64)</a></h2>
<p>Dynamic linking basically works via one indirect jump. It uses a combination of
function trampolines (<code>.plt</code> section) and a function pointer table (<code>.got.plt</code>