How to split a string literal across multiple lines in C / Objective-C?

user_77449 0
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I have a pretty long sqlite query:

const char *sql_query = "SELECT statuses.word_id FROM lang1_words, statuses WHERE statuses.word_id = lang1_words.word_id ORDER BY lang1_words.word ASC";

How can I break it in a number of lines to make it easier to read? If I do the following:

const char *sql_query = "SELECT word_id
                        FROM table1, table2
                        WHERE table2.word_id = table1.word_id
                        ORDER BY table1.word ASC";

I am getting an error.

Is there a way to write queries in multiple lines?

string-literals objective-c c
9 Answers

There are two ways to split strings over multiple lines:

  1. Each string on its own line. Works only with strings:

    • Plain C:

      char *my_string = "Line 1 "
                  "Line 2";

    • Objective-C:

      NSString *my_string = @"Line1 "
                       "Line2";    // the second @ is optional

  2. Using \ - can be used for any expression:

    • Plain C:

      char *my_string = "Line 1 \
                   Line 2";

    • Objective-C:

      NSString *my_string = @"Line1 \
                        Line2";

The first approach is better, because there isn't a lot of whitespace included. For a SQL query however, both are possible.

NOTE: With a #define, you have to add an extra \ to concatenate the two strings:

Plain C:

#define kMyString "Line 1"\
                  "Line 2"
user_245870

GCC adds C++ multiline raw string literals as a C extension

C++11 has raw string literals as mentioned at: https://stackoverflow.com/a/44337236/895245

However, GCC also adds them as a C extension, you just have to use -std=gnu99 instead of -std=c99. E.g.:

main.c

#include <assert.h>
#include <string.h>

int main(void) {
    assert(strcmp(R"(
a
b
)", "\na\nb\n") == 0);
}

Compile and run:

gcc -o main -pedantic -std=gnu99 -Wall -Wextra main.c
./main

This can be used for example to insert multiline inline assembly into C code: How to write multiline inline assembly code in GCC C++?

Now you just have to lay back, and wait for it to be standardized on C20XY.

C++ was asked at: C++ multiline string literal

Tested on Ubuntu 16.04, GCC 6.4.0, binutils 2.26.1.

user_8952450

An alternative is to use any tool for removing line breaks. Write your string using any text editor, once you finished, paste your text here and copy it again in xcode.

user_117861360
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