[clang][analyzer] Formatting of macros absent in plist reports

[ankurkraj]

While performing static analysis using Clang analyzer, the plist reports contains macros that present in the bug path of a particular report. These macros are not formatted properly and are presented as is. This often makes them unreadable in case they are large and covoluted . For eg.

For the file

#include <stdio.h>

#define dummy_unformatted   \
do {                         \
  int x = 1;                 \
  int y = 2;                 \
  if (x < y) {            \
    printf("unformatted macro with bad spacing\n");                        \
  }                        \
} while (0)

#define DIVISION(a, b) (a / b)

int demo_function(int a, int b) { 

    dummy_unformatted;
    printf("DIVISON of %d / %d is: %d\n", a, b, DIVISION(a,b));
    return 0;
}

int main(){
    int num1 = 10;
    int num2 = 0;

    demo_function(num1, num2);

    return 0;
}

The macro_expansions displayed on running analysis is

<key>expansion</key>
<key>expansion</key><string>do {int x =1;int y =2;if (x &lt;y ){printf (&quot;unformatted macro with bad spacing\n&quot;);}}while (0)</string>
<key>location</key>
<dict>

The command used to run the analysis is

clang --analyze -Xclang -analyzer-output=plist  -Xclang -analyzer-config -Xclang expand-macros=true  -I. file1.c

Ideally it should display something more readable

<key>expansion</key>
<string>do {
  int x = 1;
  int y = 2;
  if (x &lt; y) {
    printf(&quot;unformatted macro with bad spacing\n&quot;);
  }
} while (0)</string>
<key>location</key>
<dict>

It would be really helpful if there was a command line option to turn on macro formating in the plist files.

If there is no problem, I intend to work on this issue.

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

Author: None (ankurkraj)

While performing static analysis using Clang analyzer, the plist reports contains macros that present in the bug path of a particular report. These macros are not formatted properly and are presented as is. This often makes them unreadable in case they are large and covoluted . For eg.

For the file

#include <stdio.h>

#define dummy_unformatted   \
do {                         \
  int x = 1;                 \
  int y = 2;                 \
  if (x < y) {            \
    printf("unformatted macro with bad spacing\n");                        \
  }                        \
} while (0)

#define DIVISION(a, b) (a / b)

int demo_function(int a, int b) { 

    dummy_unformatted;
    printf("DIVISON of %d / %d is: %d\n", a, b, DIVISION(a,b));
    return 0;
}

int main(){
    int num1 = 10;
    int num2 = 0;

    demo_function(num1, num2);

    return 0;
}

The macro_expansions displayed on running analysis is

<key>expansion</key>
<key>expansion</key><string>do {int x =1;int y =2;if (x <y ){printf ("unformatted macro with bad spacing\n");}}while (0)</string>
<key>location</key>
<dict>

The command used to run the analysis is

clang --analyze -Xclang -analyzer-output=plist  -Xclang -analyzer-config -Xclang expand-macros=true  -I. file1.c

Ideally it should display something more readable

<key>expansion</key>
<string>do {
  int x = 1;
  int y = 2;
  if (x < y) {
    printf("unformatted macro with bad spacing\n");
  }
} while (0)</string>
<key>location</key>
<dict>

It would be really helpful if there was a command line option to turn on macro formating in the plist files.

If there is no problem, I intend to work on this issue.

[steakhal]

Hi, I'm the one responsible for this seemingly messed up formatting.
I'd suggest you reading the following resources before starting the work on this to understand the full context.
https://reviews.llvm.org/D93222 (which was committed as 6e30710).
And the child patches, mentioned in the D93222 patch. Maybe also the issues linked there too.

I'd agree with you that ideally we had nicely formatted macro expansions.
In practice, it seems to be a bit tricky to implement, because macros can be surprisingly ugly.

However, I think we could just pass these expanded tokens into clang-format to get a slightly more readable printing for the 99.9% of the cases when some sensible macros were expanded.
To have an idea how ugly macro expansions this thin should work, have a look at the test sections of the linked commits.
Mind that you might not be able to unsee what you see there.