From f2f3b3145bdc360437dfd2a0832f3e6893c3682e Mon Sep 17 00:00:00 2001
From: Aaron Taylor <ataylor@subgeniuskitty.com>
Date: Sun, 3 Jan 2021 21:46:16 -0800
Subject: [PATCH] Removed page documenting a GCC bug that has since been fixed.

---
 .../modern_c_software_development/gcc_bugs.md | 88 -------------------
 .../gcc_bugs.metadata                         |  6 --
 2 files changed, 94 deletions(-)
 delete mode 100644 data/development/pdp-11/modern_c_software_development/gcc_bugs.md
 delete mode 100644 data/development/pdp-11/modern_c_software_development/gcc_bugs.metadata

diff --git a/data/development/pdp-11/modern_c_software_development/gcc_bugs.md b/data/development/pdp-11/modern_c_software_development/gcc_bugs.md
deleted file mode 100644
index e0c6b67..0000000
--- a/data/development/pdp-11/modern_c_software_development/gcc_bugs.md
+++ /dev/null
@@ -1,88 +0,0 @@
-# Overview #
-
-Although GCC claims to support PDP-11 targets there are some bugs that must be
-worked around both in GCC and the GNU assembler.
-
-# GNU binutils Bugs #
-
-## Problem Description ##
-
-One of the addressing modes supported by the PDP-11 is 'index deferred',
-represented by `@X(Rn)`. This operand indicates that `Rn` contains a pointer
-which should be dereferenced and the result added to `X` to generate a new
-pointer to the final location. For example, consider the following four values,
-one stored in a register and the other three in memory. Then `@2(R1)` is the
-value `222`.
-
-    R1: 1000
-    1000: 2000
-    2000: 111
-    2002: 222
-
-Similarly, `@0(R1)` is the value `111`. In most PDP-11 assemblers, including
-DEC's MACRO-11 assembler, the string `@(Rn)` is an alias to `@0(Rn)`. But when
-the GNU assembler encounters `@(Rn)` it assembles it as though it were `(Rn)`,
-a single level of indirection instead of two levels!
-
-If we're only writing assembly then we can work around this bug by always using
-the form `@0(Rn)`. But what if we're writing C and using GCC to compile it?
-Consider the following C code example, taken directly from some stack-based
-debugger code written for the PDP-11.
-
-    uint16_t ** csp = (uint16_t **) 070000;
-    *csp = (uint16_t *) 060000;
-    **csp = 0;
-
-When GCC transpiles this to assembly it generates code of the form `@(Rn)` when
-assigning a value to `**csp` thus causing the value `0` to overwrite the value
-`060000` at `*csp` if GNU `as` is used to assemble the code.
-
-## Solution Description ##
-
-The following patch, tested on GNU binutils 2.28, fixes the bug. Since it
-overloads the `operand->code` variable to pass unrelated state information to
-`parse_reg()` I haven't submitted it for inclusion in GNU binutils. Once I'm
-done bug-hunting in my toolchain I will clean up all the fixes and submit them
-in one bundle.
-
-    --- tc-pdp11.c	2017-06-24 22:33:00.260210000 -0700
-    +++ tc-pdp11.c.fixed	2017-06-24 22:32:12.455205000 -0700
-    @@ -431,6 +431,9 @@
-     {
-       LITTLENUM_TYPE literal_float[2];
-     
-    +  /* Store the value (if any) passed by parse_op_noreg() before parse_reg() overwrites it. */
-    +  int deferred = operand->code;
-    +
-       str = skip_whitespace (str);
-     
-       switch (*str)
-    @@ -451,6 +454,15 @@
-     	  operand->code |= 020;
-     	  str++;
-     	}
-    +      /*
-    +       * This catches the case where @(Rn) is interpreted as (Rn) rather than @0(Rn)
-    +       */
-    +      else if (deferred)
-    +        {
-    +          operand->additional = 1;
-    +          operand->word = 0;
-    +          operand->code |= 060;
-    +        }
-           else
-     	{
-     	  operand->code |= 010;
-    @@ -581,6 +593,12 @@
-     
-       if (*str == '@' || *str == '*')
-         {
-    +      /*
-    +       * operand->code is overwritten by parse_reg() inside parse_op_no_deferred()
-    +       * We use it to temporarily catch the alias @(Rn) -> @0(Rn) since
-    +       *   parse_op_no_deferred() starts at str+1 and thus misses the '@'.
-    +       */
-    +      operand->code |= 010;
-           str = parse_op_no_deferred (str + 1, operand);
-           if (operand->error)
-    return str;
diff --git a/data/development/pdp-11/modern_c_software_development/gcc_bugs.metadata b/data/development/pdp-11/modern_c_software_development/gcc_bugs.metadata
deleted file mode 100644
index 0df03fb..0000000
--- a/data/development/pdp-11/modern_c_software_development/gcc_bugs.metadata
+++ /dev/null
@@ -1,6 +0,0 @@
-[DEFAULT]
-page_title = GCC PDP-11 Cross-Compiling Bugs
-meta_keywords = 
-meta_description = 
-menu_text = GCC Bugs
-menu_priority =
-- 
2.20.1