Incorrect #line directives cause Perl warnings

[cesaro]

Having incorrect #line directives on the input C files causes geninfo --filter trivial to call the Perl function containsTrivialFunction in a way where variable $src on lcovutil.pm:5372 is undefined. Probably lcov should gracefully handle these wrong inputs.

Example:

$ cat -n a.c
     1  // this file has 1 line
$ cat -n b.c
     1  #line 1 "a.c"
     2
     3  int fun() { return 1; }

Note that the directive #line 1 "a.c" wrongly indicates that fun was defined on a.c line 2, when in fact a.c has only 1 line. Now run:

$ gcc -c --coverage b.c
$ geninfo . -i --filter trivial,range -o out
Found gcov version: 12.3.0
Using intermediate gcov format
geninfo: WARNING: (usage) branch filter enabled but branch coverage not enabled
        (use "geninfo --ignore-errors usage,usage ..." to suppress this warning)
Recording 'internal' directories:
        /path/to/dir
Writing temporary data to /tmp/geninfo_datwbiG
Scanning . for .gcno files ...
Found 1 graph files in .
using: chunkSize: 1, nchunks:1, intervalLength:0
Finished processing 1 GCNO file
Apply filtering..
geninfo: WARNING: Use of uninitialized value $src in scalar chomp
geninfo: WARNING: Use of uninitialized value $src in substitution (s///)
geninfo: WARNING: Use of uninitialized value $src in substitution (s///)
geninfo: WARNING: Use of uninitialized value $src in concatenation (.) or string
geninfo: WARNING: Use of uninitialized value $src in scalar chomp
geninfo: WARNING: Use of uninitialized value $src in substitution (s///)
geninfo: WARNING: Use of uninitialized value $src in substitution (s///)
geninfo: WARNING: Use of uninitialized value $src in concatenation (.) or string
Finished filter file processing
Finished .info-file creation
Summary coverage rate:
  source files: 1
  lines.......: no data found
  functions...: no data found
Filter suppressions 'range':
    3 instances
    2 coverpoints
Message summary:
  1 warning message:
    usage: 1

This situation can be triggered by buggy versions of flex:

$ cat -n lex.l
     1  %%
     2  %%
     3  int fun() { return 1; }
$ flex --version
flex 2.5.37
$ flex -o lex.c lex.l
$ cat -n lex.c | tail -n 5
  1716  #line 2 "lex.l"
  1717
  1718
  1719  int fun() { return 1; }
  1720

Note that lex.c suggests that fun is defined in line 4 of lex.l, when in reality it was defined in line 3. This is was a flex bug that is fixed as of (at least) version 2.6.2 of flex, but which IMHO, should not trigger further noise in lcov.