[llvm-bugs] [Bug 24592] New: Cannot find the right back trace of the macro expansion

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=24592

            Bug ID: 24592
           Summary: Cannot find the right back trace of the macro
                    expansion
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: zhengkai at google.com
                CC: llvm-bugs at lists.llvm.org, rtrieu at google.com
    Classification: Unclassified

In /llvm/tools/clang/test/Misc/caret-diags-macros.c
#line 204
#define sprintf2(str, ...) \
  __builtin___sprintf_chk (str, 0, __darwin_obsz(str), __VA_ARGS__)
#define Cstrlen(a)  strlen_test(a)
#define Csprintf    sprintf2
void f(char* pMsgBuf, char* pKeepBuf) {
Csprintf(pMsgBuf,"\nEnter minimum anagram length (2-%1d): ",
Cstrlen(pKeepBuf));

The error message is :
warning: format specifies type 'int' but the argument has type 'unsigned long'
Csprintf(pMsgBuf,"\nEnter minimum anagram length (2-%1d): ",
Cstrlen(pKeepBuf));
                                                    ~~~      ^
                                                    %1lu

Should be 

warning: format specifies type 'int' but the argument has type 'unsigned long'
Csprintf(pMsgBuf,"\nEnter minimum anagram length (2-%1d): ",
Cstrlen(pKeepBuf));
                                                    ~~~      ^~~~~~~~~~~~~~~~~
                                                    %1lu


This bug is caused in /llvm/tools/clang/lib/Frontend/DiagnosticRenderer.cpp

in the procedure void DiagnosticRenderer::emitCaret, the procedure used
function void mapDiagnosticRanges.
This function doesn't map the right spelling ranges for the ranges given.

In the new version of this function (), the output is:

warning: format specifies type 'int' but the argument has type 'unsigned long'
Csprintf(pMsgBuf,"\nEnter minimum anagram length (2-%1d): ",
Cstrlen(pKeepBuf));
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
                                                    %1lu

This is caused by the argument Ranges which is passed to the procedure 
void DiagnosticRenderer::emitCaret indicates that the underlined part should be 
#define Cstrlen(a)  strlen_test(a)
                    ~~~~~~~~~~~~~~

But there is a kind of high-level macro invocation here. Csprintf is a macro
and it expand to sprintf2 which is a new macro name. So it continues to expand
the macro sprintf2.
So when  I trace back the range in the macro expansion stack, the range map
backs to the 
#define Csprintf    sprintf2
        ~~~~~~~~
So it finally map backs to the entire macro invocation.

I think the essential cause of this bug is that the back trace algorithm of the
macro expansions is not right in the SourceManager Class.

May be due to a similar reason with the bug:
https://llvm.org/bugs/show_bug.cgi?id=16799

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