Refactor "complex & slow"

slides.tex

@@ -56,6 +56,10 @@
     morekeywords={gdb},
     sensitive=false,
 }
+\lstdefinelanguage{cfiasm}{
+    morekeywords={cfi_startproc,cfi_def_cfa_offset,cfi_offset,cfi_def_cfa_register},
+    sensitive=false,
+}
 
 \setbeamertemplate{footline}
 {
@@ -237,14 +241,58 @@ Segmentation fault.
     \end{lstlisting}
 
     \pause{}
+    \vfill
 
     \begin{itemize}
         \item[\textbf{$\longrightarrow$}] \textbf{\alert{constructed} on-demand
             by a \alert{Turing-complete stack machine}!}
     \end{itemize}
+\end{frame}
+
+\begin{frame}{What does this imply?}
+    Your compiler actually generates codes for \alert{two machines}: your
+        processor and the DWARF VM\@.
+
+    \vfill{}
+    \begin{columns}
+        \begin{column}{0.5\textwidth}
+            \begin{center}
+                \begin{tikzpicture}
+                    \begin{scope}[every node/.style={rectangle,thick,draw,scale=0.95}]
+                        \node (cmd) at (0, 2.5) {
+                            \lstbash{\$ gcc -S foo.c}
+                        };
+                        \node (asm) at (0, 0) {
+                            \lstinputlisting[numbers=none, language=cfiasm]{src/main_cfi.s}
+                        };
+                    \end{scope}
+                    \begin{scope}[>={Stealth[black]},
+                        every path/.style={draw=black,very thick}]
+                        \path [->] (cmd) -- (asm);
+                    \end{scope}
+                \end{tikzpicture}
+                \medskip{}
+
+                \textbf{The \lstc{.cfi_*} is inline DWARF!}
+            \end{center}
+        \end{column}
+
+        \begin{column}{0.5\textwidth}
+            \begin{center}
+                \bf
+                $\implies$ if you write inline asm, you must write inline DWARF!
+            \end{center}
+
+            In \prog{glibc}, \prog{lowlevellock.h}:
+            \alert{off by one error in unwinding data}. Result:
+
+            \lstinputlisting[language=gdb,numbers=none]{src/lowlevellock_backtrace}
+        \end{column}
+    \end{columns}
+
 
     \only<2->{
-        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.17\paperheight)%
+        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.10\paperheight)%
             \begin{tcolorbox}[halign=center, colframe=red, colback=Lavender]
                 \bf \huge
                 Complex \,\& \,slow
@@ -253,13 +301,15 @@ Segmentation fault.
     }
 
     \only<3->{
-        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.35\paperheight)%
+        \begin{textblock*}{0.90\textwidth}[0.5,0](0.5\paperwidth,0.30\paperheight)%
             \begin{tcolorbox}[halign=center, colframe=red, colback=Lavender]
                 \huge
-                \textbf{Pervasive:}\\ relied upon by debuggers, profilers, C++
+                \textbf{Pervasive:}\\ relied upon by debuggers, profilers,
-                exceptions \\
+                aaand\ldots{}
+                \onslide<4->{
+                    C++ exceptions. \\
                     \medskip{}
-                \textbf{$\leadsto$ not only for debuggers!}
+                \textbf{$\leadsto$ not only for debuggers!}}
             \end{tcolorbox}
         \end{textblock*}
     }