libexpr: split yacc prologue & epilogue (NFC)

This is an NFC PR that splits epilogue & prologue from parser.

As mentioned in #8812, we can add static checking tools & auto
formatting for these files, but if it is written .y directly, the clang
parser cannot understand the code is actually "C++".

Author: inclyc

src/libexpr/lexer.l renamed to src/libexpr/lexer/lexer.l

@@ -15,98 +15,7 @@
 
 
 %{
-#ifdef __clang__
-#pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
-#endif
-
-#include <boost/lexical_cast.hpp>
-
-#include "nixexpr.hh"
-#include "parser-tab.hh"
-
-using namespace nix;
-
-namespace nix {
-
-static inline PosIdx makeCurPos(const YYLTYPE & loc, ParseData * data)
-{
-    return data->state.positions.add(data->origin, loc.first_line, loc.first_column);
-}
-
-#define CUR_POS makeCurPos(*yylloc, data)
-
-// backup to recover from yyless(0)
-thread_local YYLTYPE prev_yylloc;
-
-static void initLoc(YYLTYPE * loc)
-{
-    loc->first_line = loc->last_line = 1;
-    loc->first_column = loc->last_column = 1;
-}
-
-static void adjustLoc(YYLTYPE * loc, const char * s, size_t len)
-{
-    prev_yylloc = *loc;
-
-    loc->first_line = loc->last_line;
-    loc->first_column = loc->last_column;
-
-    for (size_t i = 0; i < len; i++) {
-       switch (*s++) {
-       case '\r':
-           if (*s == '\n') { /* cr/lf */
-               i++;
-               s++;
-           }
-           /* fall through */
-       case '\n':
-           ++loc->last_line;
-           loc->last_column = 1;
-           break;
-       default:
-           ++loc->last_column;
-       }
-    }
-}
-
-
-// we make use of the fact that the parser receives a private copy of the input
-// string and can munge around in it.
-static StringToken unescapeStr(SymbolTable & symbols, char * s, size_t length)
-{
-    char * result = s;
-    char * t = s;
-    char c;
-    // the input string is terminated with *two* NULs, so we can safely take
-    // *one* character after the one being checked against.
-    while ((c = *s++)) {
-        if (c == '\\') {
-            c = *s++;
-            if (c == 'n') *t = '\n';
-            else if (c == 'r') *t = '\r';
-            else if (c == 't') *t = '\t';
-            else *t = c;
-        }
-        else if (c == '\r') {
-            /* Normalise CR and CR/LF into LF. */
-            *t = '\n';
-            if (*s == '\n') s++; /* cr/lf */
-        }
-        else *t = c;
-        t++;
-    }
-    return {result, size_t(t - result)};
-}
-
-
-}
-
-#define YY_USER_INIT initLoc(yylloc)
-#define YY_USER_ACTION adjustLoc(yylloc, yytext, yyleng);
-
-#define PUSH_STATE(state) yy_push_state(state, yyscanner)
-#define POP_STATE() yy_pop_state(yyscanner)
-
+#include "lexer/prologue.inc"
 %}
 
 

src/libexpr/lexer/prologue.inc

@@ -0,0 +1,93 @@
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
+#endif
+
+#include <boost/lexical_cast.hpp>
+
+#include "nixexpr.hh"
+#include "parser-tab.hh"
+
+using namespace nix;
+
+namespace nix {
+
+static inline PosIdx makeCurPos(const YYLTYPE & loc, ParseData * data)
+{
+    return data->state.positions.add(data->origin, loc.first_line, loc.first_column);
+}
+
+#define CUR_POS makeCurPos(*yylloc, data)
+
+// backup to recover from yyless(0)
+thread_local YYLTYPE prev_yylloc;
+
+static void initLoc(YYLTYPE * loc)
+{
+    loc->first_line = loc->last_line = 1;
+    loc->first_column = loc->last_column = 1;
+}
+
+static void adjustLoc(YYLTYPE * loc, const char * s, size_t len)
+{
+    prev_yylloc = *loc;
+
+    loc->first_line = loc->last_line;
+    loc->first_column = loc->last_column;
+
+    for (size_t i = 0; i < len; i++) {
+        switch (*s++) {
+        case '\r':
+            if (*s == '\n') { /* cr/lf */
+                i++;
+                s++;
+            }
+            /* fall through */
+        case '\n':
+            ++loc->last_line;
+            loc->last_column = 1;
+            break;
+        default:
+            ++loc->last_column;
+        }
+    }
+}
+
+// we make use of the fact that the parser receives a private copy of the input
+// string and can munge around in it.
+static StringToken unescapeStr(SymbolTable & symbols, char * s, size_t length)
+{
+    char * result = s;
+    char * t = s;
+    char c;
+    // the input string is terminated with *two* NULs, so we can safely take
+    // *one* character after the one being checked against.
+    while ((c = *s++)) {
+        if (c == '\\') {
+            c = *s++;
+            if (c == 'n')
+                *t = '\n';
+            else if (c == 'r')
+                *t = '\r';
+            else if (c == 't')
+                *t = '\t';
+            else
+                *t = c;
+        } else if (c == '\r') {
+            /* Normalise CR and CR/LF into LF. */
+            *t = '\n';
+            if (*s == '\n')
+                s++; /* cr/lf */
+        } else
+            *t = c;
+        t++;
+    }
+    return {result, size_t(t - result)};
+}
+
+}
+
+#define YY_USER_INIT initLoc(yylloc)
+#define YY_USER_ACTION adjustLoc(yylloc, yytext, yyleng);
+
+#define PUSH_STATE(state) yy_push_state(state, yyscanner)
+#define POP_STATE() yy_pop_state(yyscanner)

src/libexpr/local.mk

@@ -28,10 +28,10 @@ libexpr_LDFLAGS_PROPAGATED = $(BDW_GC_LIBS)
 
 libexpr_ORDER_AFTER := $(d)/parser-tab.cc $(d)/parser-tab.hh $(d)/lexer-tab.cc $(d)/lexer-tab.hh
 
-$(d)/parser-tab.cc $(d)/parser-tab.hh: $(d)/parser.y
+$(d)/parser-tab.cc $(d)/parser-tab.hh: $(d)/parser/parser.y $(d)/parser/prologue.inc $(d)/parser/epilogue.inc
 	$(trace-gen) bison -v -o $(libexpr_DIR)/parser-tab.cc $< -d
 
-$(d)/lexer-tab.cc $(d)/lexer-tab.hh: $(d)/lexer.l
+$(d)/lexer-tab.cc $(d)/lexer-tab.hh: $(d)/lexer/lexer.l $(d)/lexer/prologue.inc
 	$(trace-gen) flex --outfile $(libexpr_DIR)/lexer-tab.cc --header-file=$(libexpr_DIR)/lexer-tab.hh $<
 
 clean-files += $(d)/parser-tab.cc $(d)/parser-tab.hh $(d)/lexer-tab.cc $(d)/lexer-tab.hh