Issue 15070043: code review 15070043: cmd/cgo: stop using compiler error message text to anal... (Closed)
Descriptioncmd/cgo: stop using compiler error message text to analyze C names
The old approach to determining whether "name" was a type, constant,
or expression was to compile the C program
name;
and scan the errors and warnings generated by the compiler.
This requires looking for specific substrings in the errors and warnings,
which ties the implementation to specific compiler versions.
As compilers change their errors or drop warnings, cgo breaks.
This happens slowly but it does happen.
Clang in particular (now required on OS X) has a significant churn rate.
The new approach compiles a slightly more complex program
that is either valid C or not valid C depending on what kind of
thing "name" is. It uses only the presence or absence of an error
message on a particular line, not the error text itself. The program is:
// error if and only if name is undeclared
void f1(void) { typeof(name) *x; }
// error if and only if name is not a type
void f2(void) { name *x; }
// error if and only if name is not an integer constant
void f3(void) { enum { x = (name)*1 }; }
I had not been planning to do this until Go 1.3, because it is a
non-trivial change, but it fixes a real Xcode 5 problem in Go 1.2,
and the new code is easier to understand than the old code.
It should be significantly more robust.
Fixes issue 6596.
Fixes issue 6612.
Patch Set 1 #Patch Set 2 : diff -r e7ddf900fd19 https://code.google.com/p/go/ #Patch Set 3 : diff -r e7ddf900fd19 https://code.google.com/p/go/ #
Total comments: 2
Patch Set 4 : diff -r e7ddf900fd19 https://code.google.com/p/go/ #Patch Set 5 : diff -r e7ddf900fd19 https://code.google.com/p/go/ #
Total comments: 4
Patch Set 6 : diff -r 95336afd420c https://code.google.com/p/go/ #
MessagesTotal messages: 15
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