More about how logical exp and JMP are handled. Function and UpVal.

CodeConvention.txt

@@ -16,4 +16,5 @@ LuaS	String-related API
 LuaT	Meta-table-related API
 
 LuaL	Util
-luaG	Debug
+LuaG	Debug
+LuaM	Memory

lcode.c

@@ -211,6 +211,16 @@ patchlistaux(fs, fs->jpc, fs->pc, NO_REG, fs->pc)
 
 
 
+static int code_label (FuncState *fs, int A, int b, int jump)
+==========================================================================
+Emit the last two instructions for a logical expression, one for the case the yielded
+value is TRUE, the other for FALSE.
+
+All sub-expressions in the same logical expression, which yield non-bollean values,
+jumps to the instruction following the last instruction generated by this function.
+The location of that instruction (the one following the last) is called "vtarget".
+
+
 
 static void patchlistaux (FuncState *fs, int list, int vtarget, int reg, int dtarget)
 ==========================================================================

lfunc.c

@@ -7,3 +7,9 @@ Close all open upvals when a block is out of execution flow.
 - Upvals belonging to the about-to-exit block has the "v" field higher than "level".
 - "level" is the base of a function call, or the nactvar of a block.
   ("nactvar" is the number of active locals outside a block.)
+
+This function is invoked in two places:
+- Returning from a function. (OP_RETURN)
+- Exit a block in which some local variables are used as UpVals. Whether there being any
+  variables in a block are used UpVals is determined by BlockCnt::upval and BlockCnt::prev. (OP_JMP)
+  BockCnt::prev is used to determine if it is the topmost level in a chunck (i.e. loaded source code).

lparser.c

@@ -285,6 +285,7 @@ VFALSE		|
 VK 			|
 VKFLT 		|
 VKINT 		|
+VJMP:			The expression is a comparison expression (i.e. EQ, LT, LE, NE, GE, GT).
 VRELOCABLE:		The target register (usually R(A)) is not yet determined (set as 0).
 				The instruction is already put into Proto.
 				e->u.info stores the location of the instruction.