[binutils-gdb] [gdb/testsuite] Fix error handling in _dap_read_json

[binutils-gdb] [gdb/testsuite] Fix error handling in _dap_read_json

[Tom de Vries]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=99eeecc8d276e5af745e48825d66efff693a7678

commit 99eeecc8d276e5af745e48825d66efff693a7678
Author: Tom de Vries <tdevries@suse.de>
Date:   Wed Feb 21 14:25:31 2024 +0100

    [gdb/testsuite] Fix error handling in _dap_read_json
    
    In _dap_read_json we have a gdb_expect with clauses that generate errors:
    ...
            timeout {
                error "timeout reading json header"
            }
            eof {
                error "eof reading json header"
            }
    ...
    
    Proc gdb_expect uses dejagnu's remote_expect, which has some peculiar
    semantics related to errors:
    ...
     # remote_expect works basically the same as standard expect, but it
     # also takes care of getting the file descriptor from the specified
     # host and also calling the timeout/eof/default section if there is an
     # error on the expect call.
    .....
    
    When a timeout triggers, it generates a timeout error, which is reported by
    gdb_expect, after which it runs the timeout/eof/default clauses, which
    generates an eof error, which is reported by runtest.
    
    I think the intention here is to generate just a one error, a timeout error.
    
    Fix this by postponing generating the error until after gdb_expect.
    
    Tested on x86_64-linux, by:
    - running all the DAP test-cases and observing no regressions, and
    - modifying the gdb.dap/eof.exp test-case to trigger a timeout error, and
      observing only a timeout error.
    
    PR testsuite/31382
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31382

Diff:
---
 gdb/testsuite/lib/dap-support.exp | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/gdb/testsuite/lib/dap-support.exp b/gdb/testsuite/lib/dap-support.exp
index 31f036eddf2..38b00693790 100644
--- a/gdb/testsuite/lib/dap-support.exp
+++ b/gdb/testsuite/lib/dap-support.exp
@@ -147,6 +147,8 @@ proc dap_send_request {command {obj {}}} {
 # "last_ton" will be set to the TON form of the result.
 proc _dap_read_json {} {
     set length ""
+    set seen_timeout 0
+    set seen_eof 0
     gdb_expect {
 	-re "^Content-Length: (\[0-9\]+)\r\n" {
 	    set length $expect_out(1,string)
@@ -160,13 +162,20 @@ proc _dap_read_json {} {
 	    # Done.
 	}
 	timeout {
-	    error "timeout reading json header"
+	    set seen_timeout 1
 	}
 	eof {
-	    error "eof reading json header"
+	    set seen_eof 1
 	}
     }
 
+    if {$seen_timeout} {
+	error "timeout reading json header"	
+    }
+    if {$seen_eof} {
+	error "eof reading json header"
+    }
+
     if {$length == ""} {
 	error "didn't find content-length"
     }
@@ -176,17 +185,27 @@ proc _dap_read_json {} {
 	# Tcl only allows up to 255 characters in a {} expression in a
 	# regexp, so we may need to read in chunks.
 	set this_len [expr {min ($length, 255)}]
+	set seen_timeout 0
+	set seen_eof 0
 	gdb_expect {
 	    -re "^.{$this_len}" {
 		append json $expect_out(0,string)
 	    }
 	    timeout {
-		error "timeout reading json body"
+		set seen_timeout 1
 	    }
 	    eof {
-		error "eof reading json body"
+		set seen_eof 1
 	    }
 	}
+
+	if {$seen_timeout} {
+	    error "timeout reading json header"	
+	}
+	if {$seen_eof} {
+	    error "eof reading json header"
+	}
+
 	incr length -$this_len
     }