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| author | Kaz Kylheku <kaz@kylheku.com> | 2021-04-20 04:36:05 -0700 |
|---|---|---|
| committer | Kaz Kylheku <kaz@kylheku.com> | 2021-04-20 04:36:05 -0700 |
| commit | d467598989bcd815adf30e42f9a67a73929f9d71 (patch) | |
| tree | 2c4f39c4ab225bda9c409e2db90a319aedccc3bc /HACKING | |
| parent | 1b78b60d156e3c8593efdc04133131bfcaffaeab (diff) | |
| download | txr-d467598989bcd815adf30e42f9a67a73929f9d71.tar.gz txr-d467598989bcd815adf30e42f9a67a73929f9d71.tar.bz2 txr-d467598989bcd815adf30e42f9a67a73929f9d71.zip | |
Revert bogus LIT_ALIGN commit from 2015.
This reverts commit 0343c6f32c5bd8335e88595cb9d23506625b2586.
I don't see evidence that the claim in the commit is true:
that wide literals are not four-byte-aligned on Darwin in
spite of sizeof(wchar_t) being 4. Not even with the old clang
in my old VM where I first thought I discovered this.
* configure: do not set up LIT_ALIGN == 2 for Darwin.
* lib.h (litptr): Remove LIT_ALIGN < 4 && SIZEOF_WCHAR_T == 4
case.
* HACKING: Undocument bogus claim.
Diffstat (limited to 'HACKING')
| -rw-r--r-- | HACKING | 84 |
1 files changed, 37 insertions, 47 deletions
@@ -5,44 +5,43 @@ CONTENTS: SECTION LINE -0. Overview 48 - -1. Coding Practice 55 -1.2 Program File Structure 78 -1.3 Style 92 -1.3 Error Handling 154 -1.4 I/O 167 -1.5 Type Safety 177 -1.6 Regression 219 - -2. Dynamic Types 228 -2.1 Two Kinds of Values 235 -2.1 Pointer Bitfield 246 -2.2 Heap Objects 269 -2.3 The COBJ type 289 -2.4 Strings 306 -2.4.1 Encapsulated C Strings 321 -2.4.2 Representation Hacks for 2-byte wchar_t 365 -2.4.3 Representation hacks for 4-byte wchar_t that is 2-byte aligned 423 - -3. Garbage Collection 433 -3.1 Root Pointers 451 -3.2 GC-safe Code 474 -3.2.1 Rule One: Full Initialization 500 -3.2.2 Rule Two: Make it Reachable 529 -3.3 Weak Reference Support 717 -3.4 Finalization 760 -3.5 Generational GC 784 -3.5.2 Representation of Generations 793 -3.5.3 Basic Algorithm 829 -3.5.4 Handling Backpointers 864 -3.5.5 Generational GC and Finalization 942 - -4. Debugging 971 -4.2. Debugging the Yacc-generated Parser 1102 -4.3. Debugging GC Issues 1115 -4.4 Object Breakpoint 1138 -4.5 Valgrind: Your Friend 1157 +0. Overview 47 + +1. Coding Practice 54 +1.2 Program File Structure 77 +1.3 Style 91 +1.3 Error Handling 153 +1.4 I/O 166 +1.5 Type Safety 176 +1.6 Regression 218 + +2. Dynamic Types 227 +2.1 Two Kinds of Values 234 +2.1 Pointer Bitfield 245 +2.2 Heap Objects 268 +2.3 The COBJ type 288 +2.4 Strings 305 +2.4.1 Encapsulated C Strings 320 +2.4.2 Representation Hacks for 2-byte wchar_t 364 + +3. Garbage Collection 423 +3.1 Root Pointers 441 +3.2 GC-safe Code 464 +3.2.1 Rule One: Full Initialization 490 +3.2.2 Rule Two: Make it Reachable 519 +3.3 Weak Reference Support 707 +3.4 Finalization 750 +3.5 Generational GC 774 +3.5.2 Representation of Generations 783 +3.5.3 Basic Algorithm 819 +3.5.4 Handling Backpointers 854 +3.5.5 Generational GC and Finalization 932 + +4. Debugging 961 +4.2. Debugging the Yacc-generated Parser 1092 +4.3. Debugging GC Issues 1105 +4.4 Object Breakpoint 1128 +4.5 Valgrind: Your Friend 1147 0. Overview @@ -420,15 +419,6 @@ The wref macro hides the displacement of the first character: On a platform where this hack isn't needed, these w* macros are no-ops. -2.4.3 Representation hacks for 4-byte wchar_t that is 2-byte aligned - -On the LLVM compiler on OS X, I ran into the issue that although wchar_t -is four byte aligned, the compiler neglects to make wide string literals -four byte aligned. Cases occur of misaligned literals. - -The solution is to borrow some of the logic that is used for handling -two-byte wchar_t. The data is similarly padded, and an adjustment calculation -takes place similarly to recover the pointer. 3. Garbage Collection |