[PATCH] Fix hex floating point lexing

[Tom Tromey <tom@tromey.com>]

PR gdb/18318 notes that gdb will sometimes incorrectly handle hex
floating point input.  This turns out to be a bug in the C lexer; the
'p' was not being correctly recognized, and so the exponent was not
always passed to the floating point "from_string" method.

Tested by the buildbot "Fedora-x86_64-m64" builder.

gdb/ChangeLog
2020-06-06  Tom Tromey  <tom@tromey.com>

	PR gdb/18318:
	* c-exp.y (lex_one_token): Handle 'p' like 'e'.

gdb/testsuite/ChangeLog
2020-06-06  Tom Tromey  <tom@tromey.com>

	PR gdb/18318:
	* gdb.base/printcmds.exp (test_float_accepted): Add more hex
	floating point tests.
---
 gdb/ChangeLog                        |  5 +++++
 gdb/c-exp.y                          | 11 +++++++----
 gdb/testsuite/ChangeLog              |  6 ++++++
 gdb/testsuite/gdb.base/printcmds.exp | 27 +++++++++++++++++++--------
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index e7d0a0dc4ad..5ec84eb8ed7 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -2748,7 +2748,7 @@ lex_one_token (struct parser_state *par_state, bool *is_quoted_name)
     case '9':
       {
 	/* It's a number.  */
-	int got_dot = 0, got_e = 0, toktype;
+	int got_dot = 0, got_e = 0, got_p = 0, toktype;
 	const char *p = tokstart;
 	int hex = input_radix > 10;
 
@@ -2768,13 +2768,16 @@ lex_one_token (struct parser_state *par_state, bool *is_quoted_name)
 	    /* This test includes !hex because 'e' is a valid hex digit
 	       and thus does not indicate a floating point number when
 	       the radix is hex.  */
-	    if (!hex && !got_e && (*p == 'e' || *p == 'E'))
+	    if (!hex && !got_e && !got_p && (*p == 'e' || *p == 'E'))
 	      got_dot = got_e = 1;
+	    else if (!got_e && !got_p && (*p == 'p' || *p == 'P'))
+	      got_dot = got_p = 1;
 	    /* This test does not include !hex, because a '.' always indicates
 	       a decimal floating point number regardless of the radix.  */
 	    else if (!got_dot && *p == '.')
 	      got_dot = 1;
-	    else if (got_e && (p[-1] == 'e' || p[-1] == 'E')
+	    else if (((got_e && (p[-1] == 'e' || p[-1] == 'E'))
+		      || (got_p && (p[-1] == 'p' || p[-1] == 'P')))
 		     && (*p == '-' || *p == '+'))
 	      /* This is the sign of the exponent, not the end of the
 		 number.  */
@@ -2787,7 +2790,7 @@ lex_one_token (struct parser_state *par_state, bool *is_quoted_name)
 	      break;
 	  }
 	toktype = parse_number (par_state, tokstart, p - tokstart,
-				got_dot|got_e, &yylval);
+				got_dot | got_e | got_p, &yylval);
         if (toktype == ERROR)
 	  {
 	    char *err_copy = (char *) alloca (p - tokstart + 1);
diff --git a/gdb/testsuite/gdb.base/printcmds.exp b/gdb/testsuite/gdb.base/printcmds.exp
index 066e7fce87b..05ababff78c 100644
--- a/gdb/testsuite/gdb.base/printcmds.exp
+++ b/gdb/testsuite/gdb.base/printcmds.exp
@@ -127,14 +127,25 @@ proc test_float_accepted {} {
     gdb_test "p 1.5l" " = 1.5"
 
     # Test hexadecimal floating point.
-    set test "p 0x1.1"
-    gdb_test_multiple $test $test {
-	-re " = 1\\.0625\r\n$gdb_prompt $" {
-	    pass $test
-	}
-	-re "Invalid number \"0x1\\.1\"\\.\r\n$gdb_prompt $" {
-	    # Older glibc does not support hex float, newer does.
-	    xfail $test
+    foreach {num result} {
+	0x1.1 1.0625
+	0x1.8480000000000p+6 97.125
+	0x1.8480000000000p6 97.125
+	0x00.1p0 0.0625
+	0x00.1p1 0.125
+	0x00.1p-1 0.03125
+    } {
+	set test "p $num"
+	set rxn [string_to_regexp $num]
+	set rxr [string_to_regexp $result]
+	gdb_test_multiple $test $test {
+	    -re " = $result\r\n$gdb_prompt $" {
+		pass $test
+	    }
+	    -re "Invalid number \".*\"\\.\r\n$gdb_prompt $" {
+		# Older glibc does not support hex float, newer does.
+		xfail $test
+	    }
 	}
     }
 }
-- 
2.17.2