Bug#36783534 Fix comp_sql to allow for single literal generation

  - adds an optional as_single_string argument to comp_sql script
  - if that argument is "true", then the generated header file
    will not be an array of char pointers with nullptr at the end,
    but a single constexpr const char[]
  - reason for change: in some cases this script is used to load
    non-SQL files and instead of currently concatenating all the
    literals at run-time and save them in std::string, we would
    prefer to already have a ready literal at compile time

Change-Id: Icc2c8d4623f45dcd9ea06aefa63714801bed3876

Author: Igor Pesic

scripts/comp_sql.cc

@@ -32,6 +32,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <cstring>
 
 #include "my_compiler.h"
 #include "mysql/psi/mysql_file.h"
@@ -86,7 +87,7 @@ static char *fgets_fn(char *buffer, size_t size, MYSQL_FILE *input,
   return line;
 }
 
-static void print_query(FILE *out, const char *query) {
+static void print_query(FILE *out, const char *query, bool as_single_string) {
   const char *ptr = query;
   int column = 0;
 
@@ -125,7 +126,12 @@ static void print_query(FILE *out, const char *query) {
     }
     ptr++;
   }
-  fprintf(out, "\\n\",\n");
+  if (as_single_string) {
+    // no commas, since it is a single literal
+    fprintf(out, "\\n\"\n");
+  } else {
+    fprintf(out, "\\n\",\n");
+  }
 }
 
 int main(int argc, char *argv[]) {
@@ -137,8 +143,14 @@ int main(int argc, char *argv[]) {
   size_t query_length = 0;
   bootstrap_parser_state parser_state;
 
-  if (argc != 4)
-    die("Usage: comp_sql <struct_name> <sql_filename> <c_filename>");
+  if (argc < 4 || argc > 5)
+    die("Usage: comp_sql <struct_name> <sql_filename> <c_filename> "
+        "[<as_single_string>]");
+  bool as_single_string = false;
+  if (argc == 5) {
+    char *as_single_string_arg = argv[4];
+    if (std::strcmp(as_single_string_arg, "true") == 0) as_single_string = true;
+  }
 
   /* Open input and output file */
   if (!(in = fopen(infile_name, "r")))
@@ -152,7 +164,12 @@ int main(int argc, char *argv[]) {
           "  Do not edit this file, it is automatically generated from:\n");
   fprintf(out, "  <%s>\n", infile_name);
   fprintf(out, "*/\n");
-  fprintf(out, "const char* %s[]={\n", struct_name);
+  if (as_single_string) {
+    // single literal can also be constexpr
+    fprintf(out, "constexpr const char %s[]=\n", struct_name);
+  } else {
+    fprintf(out, "const char* %s[]={\n", struct_name);
+  }
 
   parser_state.init(infile_name);
 
@@ -173,10 +190,15 @@ int main(int argc, char *argv[]) {
       parser_state.report_error_details(parser_die);
     }
 
-    print_query(out, query);
+    print_query(out, query, as_single_string);
   }
 
-  fprintf(out, "nullptr\n};\n");
+  if (as_single_string) {
+    // no need for nullptr and bracket in a single literal
+    fprintf(out, ";\n");
+  } else {
+    fprintf(out, "nullptr\n};\n");
+  }
 
   fclose(in);
   fclose(out);